intel/compiler: Do not reswizzle dst if instruction writes to flag register

If we write to the flag register changing the swizzle would change
what channels are written to the flag register.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110201


Fixes: 4cd1a0be
Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by:  <ian.d.romanick@intel.com>
(cherry picked from commit 04508f57)