ptp: ptp_ines: prevent build when HAS_IOMEM is not set

ptp_ines.c uses devm_platform_ioremap_resource(), which is only
built/available when CONFIG_HAS_IOMEM is enabled.
CONFIG_HAS_IOMEM is not enabled for arch/s390/, so builds on S390
have a build error:

s390-linux-ld: drivers/ptp/ptp_ines.o: in function `ines_ptp_ctrl_probe':
ptp_ines.c:(.text+0x17e6): undefined reference to `devm_platform_ioremap_resource'

Prevent builds of ptp_ines.c when HAS_IOMEM is not set.

Fixes: bad1eaa6 ("ptp: Add a driver for InES time stamping IP core.")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Link: lore.kernel.org/r/202101031125.ZEFCUiKi-lkp@intel.com
Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://lore.kernel.org/r/20210106042531.1351-1-rdunlap@infradead.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/ptp/Kconfig

@@ -79,6 +79,7 @@ config DP83640_PHY
 config PTP_1588_CLOCK_INES
 	tristate "ZHAW InES PTP time stamping IP core"
 	depends on NETWORK_PHY_TIMESTAMPING
+	depends on HAS_IOMEM
 	depends on PHYLIB
 	depends on PTP_1588_CLOCK
 	help