llvmpipe: Fix build with LLVM 2.8

Commit 8d9778589f added all-targets to the
LLVM_COMPONENTS list, but this component does not exist with LLVM 2.8.

Adding all-targets is not necessary for any drivers, and it seems to be
left over from earlier versions of the commit mentioned above.

Tested-by: Stéphane Marchesin <marcheu@chromium.org>

configure.ac

@@ -1661,7 +1661,7 @@ if test "x$enable_gallium_llvm" = xyes; then
             if $LLVM_CONFIG --components | grep -q '\<mcjit\>'; then
                 LLVM_COMPONENTS="${LLVM_COMPONENTS} mcjit"
             fi
-            LLVM_COMPONENTS="${LLVM_COMPONENTS} all-targets"
+
             if test "x$enable_opencl" = xyes; then
                 LLVM_COMPONENTS="${LLVM_COMPONENTS} ipo linker instrumentation"
             fi