kmemleak-test: add missing MODULE_DESCRIPTION() macro

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/kmemleak/kmemleak-test.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Link: https://lkml.kernel.org/r/20240601-md-samples-kmemleak-v1-1-47186be7f0a8@quicinc.com


Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>