i965/vec4: Fix exec size for MOVs {SET,PICK}_{HIGH,LOW}_32BIT.

i965/vec4: Fix exec size for MOVs {SET,PICK}_{HIGH,LOW}_32BIT.

Otherwise for a pack_double_2x32_split opcode, we emit:

   vec1 64 ssa_135 = pack_double_2x32_split ssa_133, ssa_134
mov(8)          g5<1>UD         g5<4>.xUD                       { align16 1Q compacted };
mov(8)          g7<2>UD         g5<4,4,1>UD                     { align1 1Q };
        ERROR: When the destination spans two registers, the source must span two registers
               (exceptions for scalar source and packed-word to packed-dword expansion)
mov(8)          g8<2>UD         g5.4<4,4,1>UD                   { align1 2N };
        ERROR: The offset from the two source registers must be the same
mov(8)          g5<1>UD         g6<4>.xUD                       { align16 1Q compacted };
mov(8)          g7.1<2>UD       g5<4,4,1>UD                     { align1 1Q };
        ERROR: When the destination spans two registers, the source must span two registers
               (exceptions for scalar source and packed-word to packed-dword expansion)
mov(8)          g8.1<2>UD       g5.4<4,4,1>UD                   { align1 2N };
        ERROR: The offset from the two source registers must be the same

The intention was to emit mov(4)s for the instructions that have ERROR
annotations.

See tests/spec/arb_gpu_shader_fp64/execution/vs-isinf-dvec.shader_test
for example.

v2 (Samuel):
- Instead of setting the exec size to a fixed value, don't double it
(Curro).
- Add PICK_{HIGH,LOW}_32BIT to the condition.

Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
[ Francisco Jerez: Trivial rebase changes. ]
Reviewed-by: Francisco Jerez <currojerez@riseup.net>