mfd: Add missing MODULE_DESCRIPTION() macros

mfd: Add missing MODULE_DESCRIPTION() macros

On x86, make allmodconfig && make W=1 C=1 reports:

 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mfd/arizona.o
 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mfd/pcf50633-gpio.o
 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mfd/timberdale.o
 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mfd/ssbi.o
 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mfd/rt4831.o
 WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/mfd/intel_soc_pmic_bxtwc.o

Add the missing invocation of the MODULE_DESCRIPTION() macro to all
files which have a MODULE_LICENSE().

This includes mfd-core.c and vexpress-sysreg.c which, although they
did not produce a warning with the x86 allmodconfig configuration, may
cause this warning with other configurations.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Acked-by: Andy Shevchenko <andy@kernel.org> # for Intel Broxton PMIC
Link: https://lore.kernel.org/r/20240609-md-drivers-mfd-v1-1-47cdd0b394e9@quicinc.com
Signed-off-by: Lee Jones <lee@kernel.org>