kfifo: add missing MODULE_DESCRIPTION() macros

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/kfifo/bytestream-example.o
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/kfifo/dma-example.o
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/kfifo/inttype-example.o
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/kfifo/record-example.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.

Link: https://lkml.kernel.org/r/20240601-md-samples-kfifo-v1-1-de34345c5fd8@quicinc.com


Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>