net: ipa: relax 64-bit build requirement

We currently assume the IPA driver is built only for a 64 bit kernel.

When this constraint was put in place it eliminated some do_div()
calls, replacing them with the "/" and "%" operators.  We now only
use these operations on u32 and size_t objects.  In a 32-bit kernel
build, size_t will be 32 bits wide, so there remains no reason to
use do_div() for divide and modulo.

A few recent commits also fix some code that assumes that DMA
addresses are 64 bits wide.

With that, we can get rid of the 64-bit build requirement.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ipa/Kconfig

 config QCOM_IPA
 	tristate "Qualcomm IPA support"
-	depends on 64BIT && NET && QCOM_SMEM
+	depends on NET && QCOM_SMEM
 	depends on ARCH_QCOM || COMPILE_TEST
 	depends on QCOM_RPROC_COMMON || (QCOM_RPROC_COMMON=n && COMPILE_TEST)
 	select QCOM_MDT_LOADER if ARCH_QCOM

drivers/net/ipa/ipa_main.c

@@ -735,8 +735,14 @@ MODULE_DEVICE_TABLE(of, ipa_match);
 static void ipa_validate_build(void)
 {
 #ifdef IPA_VALIDATE
-	/* We assume we're working on 64-bit hardware */
-	BUILD_BUG_ON(!IS_ENABLED(CONFIG_64BIT));
+	/* At one time we assumed a 64-bit build, allowing some do_div()
+	 * calls to be replaced by simple division or modulo operations.
+	 * We currently only perform divide and modulo operations on u32,
+	 * u16, or size_t objects, and of those only size_t has any chance
+	 * of being a 64-bit value.  (It should be guaranteed 32 bits wide
+	 * on a 32-bit build, but there is no harm in verifying that.)
+	 */
+	BUILD_BUG_ON(!IS_ENABLED(CONFIG_64BIT) && sizeof(size_t) != 4);
 
 	/* Code assumes the EE ID for the AP is 0 (zeroed structure field) */
 	BUILD_BUG_ON(GSI_EE_AP != 0);