mesa: Update to use llvm 6.0

Adpat to the upgrade from 5.0 -> 6.0.

(From OE-Core rev: dc52f9cf343df4c2d77bee0e47004466321e7edb)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-graphics/mesa/mesa.inc

@@ -89,7 +89,7 @@ GALLIUMDRIVERS_append_x86 = "${@bb.utils.contains('PACKAGECONFIG', 'gallium-llvm
 GALLIUMDRIVERS_append_x86-64 = "${@bb.utils.contains('PACKAGECONFIG', 'gallium-llvm', ',${GALLIUMDRIVERS_LLVM}', '', d)}"
 # keep --with-gallium-drivers separate, because when only one of gallium versions is enabled, other 2 were adding --without-gallium-drivers
 PACKAGECONFIG[gallium]      = "--enable-texture-float --with-gallium-drivers=${GALLIUMDRIVERS}, --without-gallium-drivers"
-MESA_LLVM_RELEASE ?= "5.0"
+MESA_LLVM_RELEASE ?= "6.0"
 PACKAGECONFIG[gallium-llvm] = "--enable-llvm --enable-llvm-shared-libs, --disable-llvm, llvm${MESA_LLVM_RELEASE} llvm-native \
                                ${@'elfutils' if ${GALLIUMDRIVERS_LLVM33_ENABLED} else ''}"
 export WANT_LLVM_RELEASE = "${MESA_LLVM_RELEASE}"