mfd: rsmu: Split core code into separate module

Linking a file into two modules can have unintended side-effects
and produces a W=1 warning:

scripts/Makefile.build:236: drivers/mfd/Makefile: rsmu_core.o is added to multiple modules: rsmu-i2c rsmu-spi

Make this one a separate module instead.

Fixes: a1867f85 ("mfd: Add Renesas Synchronization Management Unit (SMU) support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20240529094856.1869543-1-arnd@kernel.orgSigned-off-by: Lee Jones <lee@kernel.org>

drivers/mfd/Makefile

@@ -286,7 +286,5 @@ obj-$(CONFIG_MFD_INTEL_M10_BMC_PMCI)   += intel-m10-bmc-pmci.o
 obj-$(CONFIG_MFD_ATC260X)	+= atc260x-core.o
 obj-$(CONFIG_MFD_ATC260X_I2C)	+= atc260x-i2c.o
 
-rsmu-i2c-objs			:= rsmu_core.o rsmu_i2c.o
-rsmu-spi-objs			:= rsmu_core.o rsmu_spi.o
-obj-$(CONFIG_MFD_RSMU_I2C)	+= rsmu-i2c.o
-obj-$(CONFIG_MFD_RSMU_SPI)	+= rsmu-spi.o
+obj-$(CONFIG_MFD_RSMU_I2C)	+= rsmu_i2c.o rsmu_core.o
+obj-$(CONFIG_MFD_RSMU_SPI)	+= rsmu_spi.o rsmu_core.o

drivers/mfd/rsmu_core.c

@@ -78,11 +78,13 @@ int rsmu_core_init(struct rsmu_ddata *rsmu)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(rsmu_core_init);
 
 void rsmu_core_exit(struct rsmu_ddata *rsmu)
 {
 	mutex_destroy(&rsmu->lock);
 }
+EXPORT_SYMBOL_GPL(rsmu_core_exit);
 
 MODULE_DESCRIPTION("Renesas SMU core driver");
 MODULE_LICENSE("GPL");