i965/fs: Don't mix integer/float immediates in i2b handling.

i965/fs: Don't mix integer/float immediates in i2b handling.

The simulator gets very angry about our i2b code:

cmp.ne(16)      g3<1>D          g2<0,1,0>D      0F

We can't mix integer DWord and float types.  The only reason to use 0F
here was to share code with f2b.  Split it and use 0D instead.

While we don't believe anything bad will actually happen because of
this, it's nice to fix the warnings and easy enough to do.

Reviewed-by: Paul Berry <stereotype441@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>