hwpmc: Fix compile warning

.../sys/dev/hwpmc/hwpmc_mod.c:4640:1: warning: unused function 'pmc_is_multipart' [-Wunused-function]
 4640 | pmc_is_multipart(struct pmc_sample *ps)
      | ^~~~~~~~~~~~~~~~
1 warning generated.

Reviewed by:	mhorne
Fixes:		e51ef8ae49 - main - hwpmc: Initial support for AMD IBS
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D56296

sys/dev/hwpmc/hwpmc_mod.c

@@ -198,7 +198,6 @@ static int	pmc_debugflags_sysctl_handler(SYSCTL_HANDLER_ARGS);
 static int	pmc_debugflags_parse(char *newstr, char *fence);
 #endif
 
-static bool	pmc_is_multipart(struct pmc_sample *ps);
 static void	pmc_multipart_add(struct pmc_sample *ps, int type,
     int length);
 static void	pmc_multipart_copydata(struct pmc_sample *ps,
@@ -4636,12 +4635,6 @@ pmc_post_callchain_callback(void)
 	return;
 }
 
-static bool
-pmc_is_multipart(struct pmc_sample *ps)
-{
-	return ((ps->ps_flags & PMC_CC_F_MULTIPART) != 0);
-}
-
 static void
 pmc_multipart_add(struct pmc_sample *ps, int type, int length)
 {