isl: Don't use surface format R32_FLOAT for typed atomic integer operations

isl: Don't use surface format R32_FLOAT for typed atomic integer operations

From Skylake PRM Surface Formats section:

   "The surface format for the typed atomic integer operations must
    be R32_UINT or R32_SINT."

Fixes an error and a piglit GPU hang in simulation environment.
Piglit test: gl45-imageAtomicExchange-float.shader_test

Suggested-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.co
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "18.0 17.3" <mesa-stable@lists.freedesktop.org>