gperf: don't install to staging dir

It doesn't make much sense to install the cross-gperf to staging dir.

package/gperf/gperf.mk

@@ -7,7 +7,7 @@ GPERF_VERSION = 3.0.3
 GPERF_SOURCE = gperf-$(GPERF_VERSION).tar.gz
 GPERF_SITE = $(BR2_GNU_MIRROR)/gperf
 GPERF_AUTORECONF = NO
-GPERF_INSTALL_STAGING = YES
+GPERF_INSTALL_STAGING = NO
 GPERF_INSTALL_TARGET = YES
 GPERF_INSTALL_STAGING_OPT = DESTDIR=$(STAGING_DIR) install
 GPERF_INSTALL_TARGET_OPT = DESTDIR=$(TARGET_DIR) install