lib/test_linear_ranges: add missing MODULE_DESCRIPTION() macro

lib/test_linear_ranges: add missing MODULE_DESCRIPTION() macro

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/test_linear_ranges.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Link: https://lkml.kernel.org/r/20240531-md-lib-test_linear_ranges-v1-1-053a1aad37c6@quicinc.com
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>