toolchain/gdb: reorganize patch layout

Use ./patches and ./patches-arc instead of version dependent patches.
We should have only one main supported version (along with the special
case for arc).

Signed-off-by: Felix Fietkau <nbd@nbd.name>

toolchain/gdb/Makefile

@@ -15,6 +15,7 @@ PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/foss-for-synopsys-dwc-arc-processors/binutils-gdb/archive/arc-2016.03-gdb
 PKG_MD5SUM:=775caaf6385c16f20b6f53c0a2b95f79
 GDB_DIR:=binutils-$(PKG_NAME)-$(PKG_VERSION)
+PATCH_DIR:=./patches-arc
 else
 PKG_VERSION:=7.11
 
@@ -24,8 +25,6 @@ PKG_MD5SUM:=b5c784685e1cde65ba135feea86b6d75
 GDB_DIR:=$(PKG_NAME)-$(PKG_VERSION)
 endif
 
-PATCH_DIR:=./patches/$(PKG_VERSION)
-
 HOST_BUILD_DIR:=$(BUILD_DIR_TOOLCHAIN)/$(GDB_DIR)
 
 HOST_BUILD_PARALLEL:=1