glsl: always call do_lower_jumps() after loop unrolling

This fixes a bug in radeonsi where LLVM cannot handle the case where
a break exists but its not the last instruction in the block.

LLVM would fail with:
Terminator found in the middle of a basic block!
LLVM ERROR: Broken function found, compilation aborted!

Fixes: 96fe8834 "glsl_to_tgsi: do fewer optimizations with GLSLOptimizeConservatively"

Reviewed-by: Matt Turner <mattst88@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105317
(cherry picked from commit b42633db)