pstore: platform: add missing MODULE_DESCRIPTION() macro

With ARCH=csky, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/pstore/pstore.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240613-md-csky-fs-pstore-v1-1-c525f636b1cb@quicinc.com


Signed-off-by: Kees Cook <kees@kernel.org>