x86/mce/inject: Add missing MODULE_DESCRIPTION() line

make W=1 C=1 warns:

  WARNING: modpost: missing MODULE_DESCRIPTION() in arch/x86/kernel/cpu/mce/mce-inject.o

Add the missing MODULE_DESCRIPTION().

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240530-md-x86-mce-inject-v1-1-2a9dc998f709@quicinc.com