samples/kobject: add missing MODULE_DESCRIPTION() macros

samples/kobject: add missing MODULE_DESCRIPTION() macros

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/kobject/kobject-example.o
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/kobject/kset-example.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/20240601-md-samples-kobject-v1-1-f63b215d50cb@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>