mailbox, remoteproc: omap2+: fix compile testing

Selecting CONFIG_OMAP2PLUS_MBOX while compile testing
causes a build failure:

WARNING: unmet direct dependencies detected for OMAP2PLUS_MBOX
  Depends on [n]: MAILBOX [=y] && (ARCH_OMAP2PLUS || ARCH_K3)
  Selected by [m]:
  - TI_K3_M4_REMOTEPROC [=m] && REMOTEPROC [=y] && (ARCH_K3 || COMPILE_TEST [=y])

Using 'select' to force-enable another subsystem is generally
a mistake and causes problems such as this one, so change the
three drivers that link against this driver to use 'depends on'
instead, and ensure the driver itself can be compile tested
regardless of the platform.

When compile-testing without CONFIG_TI_SCI_PROTOCOL=m, there
is a chance for a link failure, so add a careful dependency
on that.

arm-linux-gnueabi-ld: drivers/remoteproc/ti_k3_m4_remoteproc.o: in function `k3_m4_rproc_probe':
ti_k3_m4_remoteproc.c:(.text.k3_m4_rproc_probe+0x76): undefined reference to `devm_ti_sci_get_by_phandle'

Fixes: ebcf9008 ("remoteproc: k3-m4: Add a remoteproc driver for M4F subsystem")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Andrew Davis <afd@ti.com>
Reviewed-by: Martyn Welch <martyn.welch@collabora.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

drivers/mailbox/Kconfig

@@ -74,7 +74,7 @@ config ARMADA_37XX_RWTM_MBOX
 
 config OMAP2PLUS_MBOX
 	tristate "OMAP2+ Mailbox framework support"
-	depends on ARCH_OMAP2PLUS || ARCH_K3
+	depends on ARCH_OMAP2PLUS || ARCH_K3 || COMPILE_TEST
 	help
 	  Mailbox implementation for OMAP family chips with hardware for
 	  interprocessor communication involving DSP, IVA1.0 and IVA2 in

drivers/mailbox/omap-mailbox.c

@@ -603,7 +603,7 @@ static struct platform_driver omap_mbox_driver = {
 	.driver	= {
 		.name = "omap-mailbox",
 		.pm = &omap_mbox_pm_ops,
-		.of_match_table = of_match_ptr(omap_mailbox_of_match),
+		.of_match_table = omap_mailbox_of_match,
 	},
 };
 module_platform_driver(omap_mbox_driver);

drivers/remoteproc/Kconfig

@@ -330,8 +330,7 @@ config STM32_RPROC
 config TI_K3_DSP_REMOTEPROC
 	tristate "TI K3 DSP remoteproc support"
 	depends on ARCH_K3
-	select MAILBOX
-	select OMAP2PLUS_MBOX
+	depends on OMAP2PLUS_MBOX
 	help
 	  Say m here to support TI's C66x and C71x DSP remote processor
 	  subsystems on various TI K3 family of SoCs through the remote
@@ -343,8 +342,7 @@ config TI_K3_DSP_REMOTEPROC
 config TI_K3_R5_REMOTEPROC
 	tristate "TI K3 R5 remoteproc support"
 	depends on ARCH_K3
-	select MAILBOX
-	select OMAP2PLUS_MBOX
+	depends on OMAP2PLUS_MBOX
 	help
 	  Say m here to support TI's R5F remote processor subsystems
 	  on various TI K3 family of SoCs through the remote processor