treewide: use name in define and eval lines

For consistency, use full name instead of $(PKG_NAME) in define and eval
lines for all packages.

I've seen reviews that asked to do this before, and I am asking the same
during reviews now. To avoid this in the future, fix this treewide so
when people use existing packages as example, we will not have to
request this change anymore.

This makes all packages consistent with both LEDE and OpenWrt base
repositories.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

libs/musl-fts/Makefile

@@ -30,7 +30,7 @@ PKG_INSTALL:=1
 
 include $(INCLUDE_DIR)/package.mk
 
-define Package/$(PKG_NAME)
+define Package/musl-fts
   SECTION:=libs
   CATEGORY:=Libraries
   TITLE:=fts implementation for musl libc
@@ -38,7 +38,7 @@ define Package/$(PKG_NAME)
   DEPENDS:= +libpthread
 endef
 
-define Package/$(PKG_NAME)/description
+define Package/musl-fts/description
   The musl-fts package implements the fts(3) functions fts_open, fts_read, fts_children, fts_set and fts_close, which are missing in musl libc.
 endef
 
@@ -51,9 +51,9 @@ define Build/InstallDev
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/pkgconfig/musl-fts.pc $(1)/usr/lib/pkgconfig/
 endef
 
-define Package/$(PKG_NAME)/install
+define Package/musl-fts/install
 	$(INSTALL_DIR) $(1)/usr/lib
 	$(CP) $(PKG_INSTALL_DIR)/usr/lib/libfts.so* $(1)/usr/lib/
 endef
 
-$(eval $(call BuildPackage,$(PKG_NAME)))
+$(eval $(call BuildPackage,musl-fts))