soc: imx: increase build coverage for imx8m soc driver

The soc-imx8.c driver is actually for i.MX8M family, so rename it
to soc-imx8m.c.

Use CONFIG_SOC_IMX8M as build gate, not CONFIG_ARCH_MXC, to control
whether build this driver, also make it possible for compile test.

Default set it to y for ARCH_MXC && ARM64
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/soc/Makefile

@@ -11,7 +11,7 @@ obj-$(CONFIG_ARCH_DOVE)		+= dove/
 obj-$(CONFIG_MACH_DOVE)		+= dove/
 obj-y				+= fsl/
 obj-$(CONFIG_ARCH_GEMINI)	+= gemini/
-obj-$(CONFIG_ARCH_MXC)		+= imx/
+obj-y				+= imx/
 obj-$(CONFIG_ARCH_IXP4XX)	+= ixp4xx/
 obj-$(CONFIG_SOC_XWAY)		+= lantiq/
 obj-y				+= mediatek/

drivers/soc/imx/Kconfig

@@ -17,4 +17,13 @@ config IMX_SCU_SOC
 	  Controller Unit SoC info module, it will provide the SoC info
 	  like SoC family, ID and revision etc.
 
+config SOC_IMX8M
+	bool "i.MX8M SoC family support"
+	depends on ARCH_MXC || COMPILE_TEST
+	default ARCH_MXC && ARM64
+	help
+	  If you say yes here you get support for the NXP i.MX8M family
+	  support, it will provide the SoC info like SoC family,
+	  ID and revision etc.
+
 endmenu

drivers/soc/imx/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_HAVE_IMX_GPC) += gpc.o
 obj-$(CONFIG_IMX_GPCV2_PM_DOMAINS) += gpcv2.o
-obj-$(CONFIG_ARCH_MXC) += soc-imx8.o
+obj-$(CONFIG_SOC_IMX8M) += soc-imx8m.o
 obj-$(CONFIG_IMX_SCU_SOC) += soc-imx-scu.o