draw: allow LLVM use on non-SSE2 X86 cpus

draw: allow LLVM use on non-SSE2 X86 cpus

This patch remove workaround related to LLVM < 3.2 bug.

Original bug has been closed as fixed in 2011.
At this moment gallium requires LLVM 3.3 (2013).

LLVM has been tested without SSE2 support in commit
ca70de9bd20bc4a11b2d2d368e0cc1f49527a947 and removed after requiring
LLVM 3.3 in commit 013ff2fae13da41c2f5619c4698b0a7b5aa6a06d

Original LLVM bug: http://llvm.org/bugs/show_bug.cgi?id=6960

Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>