spmi: add missing MODULE_DESCRIPTION() macros

spmi: add missing MODULE_DESCRIPTION() macros

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/spmi/hisi-spmi-controller.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/spmi/spmi-pmic-arb.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240609-md-drivers-spmi-v1-1-f1d5b24e7a66@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>