uclibc: install headers after building headers in configure part

This patch will run "make headers install_headers" instead of the old "make
headers install_dev". The latter requires a cross compiler available in uClibc
versions > 0.9.29, and the cross compiler is not available at the configuration
time of uClibc.

Spotted and fixed by Bernhard Fischer.

Tested-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>

toolchain/uClibc/uclibc.mk

@@ -434,7 +434,7 @@ $(UCLIBC_DIR)/.configured: $(LINUX_HEADERS_DIR)/.configured $(UCLIBC_DIR)/.confi
 		DEVEL_PREFIX=/usr/ \
 		RUNTIME_PREFIX=$(TOOL_BUILD_DIR)/uClibc_dev/ \
 		HOSTCC="$(HOSTCC)" \
-		headers install_dev
+		headers install_headers
 	# Install the kernel headers to the first stage gcc include dir
 	# if necessary
 ifeq ($(LINUX_HEADERS_IS_KERNEL),y)