perf/x86/rapl: Add missing MODULE_DESCRIPTION() line

Fix the warning from 'make C=1 W=1':

  WARNING: modpost: missing MODULE_DESCRIPTION() in arch/x86/events/rapl.o

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Link: https://lore.kernel.org/r/20240530-md-arch-x86-events-v1-1-e45ffa8af99f@quicinc.com