swr: Fix build with llvm-10.0.

swr: Fix build with llvm-10.0.

Fix build error after llvm-10 commit 5d986953c8b9 ("[IR] Split out
target specific intrinsic enums into separate headers").

../src/gallium/drivers/swr/rasterizer/jitter/functionpasses/lower_x86.cpp:78:37: error: ‘x86_bmi_bextr_32’ is not a member of ‘llvm::Intrinsic’
         {"meta.intrinsic.BEXTR_32", Intrinsic::x86_bmi_bextr_32},
                                     ^

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Krzysztof Raszkowski <krzysztof.raszkowski@intel.com>
Reviewed-by: Jan Zielinski <jan.zielinski@intel.com>