perf: set the perfexecdir

This allows the files installed into /usr/libexec to be
relocated to ${libexecdir}. removed unneded prefix=/usr,
which would prevent ${prefix} relocation.

(From OE-Core rev: 10d28438c1e7d793bc398a0ad484782e5baa4877)

Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-kernel/perf/perf_3.4.bb

@@ -63,7 +63,7 @@ EXTRA_OEMAKE = \
 		ARCH=${ARCH} \
 		CC="${CC}" \
 		AR="${AR}" \
-		prefix=/usr \
+		perfexecdir=${libexecdir} \
 		NO_GTK2=1 ${TUI_DEFINES} NO_DWARF=1 ${SCRIPTING_DEFINES} \
 		'