Fixes build error:
```
x86_64-openwrt-linux-musl-gcc -L/home/sandu/work/lede/staging_dir/target-x86_64_musl-1.1.15/usr/lib -L/home/sandu/work/lede/staging_dir/target-x86_64_musl-1.1.15/lib -L/home/sandu/work/lede/staging_dir/toolchain-x86_64_gcc-5.4.0_musl-1.1.15/usr/lib -L/home/sandu/work/lede/staging_dir/toolchain-x86_64_gcc-5.4.0_musl-1.1.15/lib -znow -zrelro -fPIC -shared -Wl,--version-script=libfdt/version.lds -Wl,-soname,libfdt.so.1 -o libfdt/libfdt-1.4.2.so libfdt/fdt.o libfdt/fdt_ro.o libfdt/fdt_wip.o libfdt/fdt_sw.o libfdt/fdt_rw.o libfdt/fdt_strerror.o libfdt/fdt_empty_tree.o libfdt/fdt_addresses.o
/home/sandu/work/lede/staging_dir/toolchain-x86_64_gcc-5.4.0_musl-1.1.15/lib64/gcc/x86_64-openwrt-linux-musl/5.4.0/../../../../x86_64-openwrt-linux-musl/bin/ld: libfdt/fdt.o: relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC
libfdt/fdt.o: error adding symbols: Bad value
collect2: error: ld returned 1 exit status
Makefile:283: recipe for target 'libfdt/libfdt-1.4.2.so' failed
make[4]: *** [libfdt/libfdt-1.4.2.so] Error 1
```
Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
PKG_NAME:=dtc
PKG_VERSION:=1.4.2
-PKG_RELEASE:=1
+PKG_RELEASE:=2
PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
PKG_SOURCE_URL:=https://www.kernel.org/pub/software/utils/dtc
PKG_SOURCE_MD5SUM:=3d5814e31b2046ef51fca8fece998db0
$(CP) $(PKG_INSTALL_DIR)/lib/libfdt*.so* $(1)/usr/lib
endef
+TARGET_CFLAGS += \
+ $(FPIC)
+
MAKE_FLAGS += \
PREFIX= \
CFLAGS="$(TARGET_CFLAGS)"