intel/fs: Handle source modifiers in lower_integer_multiplication().

intel/fs: Handle source modifiers in lower_integer_multiplication().

lower_integer_multiplication() implements 32x32-bit multiplication on
some platforms by bit-casting one of the 32-bit sources into two
16-bit unsigned integer portions.  This can give incorrect results if
the original instruction specified a source modifier.  Fix it by
emitting an additional MOV instruction implementing the source
modifiers where necessary.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>