mfd: Kconfig: Default MFD_SPACEMIT_P1 to 'm' if ARCH_SPACEMIT

The default value of the P1 sub-device depends on the value
of P1, so P1 should have a default value here.

Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Acked-by: Alex Elder <elder@riscstar.com>
Link: https://patch.msgid.link/20251225-p1-kconfig-fix-v4-2-44b6728117c1@linux.spacemit.com
Signed-off-by: Lee Jones <lee@kernel.org>

Author: TroyMitchell911

drivers/mfd/Kconfig

@@ -1276,6 +1276,7 @@ config MFD_SPACEMIT_P1
 	depends on ARCH_SPACEMIT || COMPILE_TEST
 	depends on I2C
 	select MFD_SIMPLE_MFD_I2C
+	default m if ARCH_SPACEMIT
 	help
 	  This option supports the I2C-based SpacemiT P1 PMIC, which
 	  contains regulators, a power switch, GPIOs, an RTC, and more.