nv50/ir: optimize neg(and(set, 1)) to set

nv50/ir: optimize neg(and(set, 1)) to set

helps shaders in saints row IV, bioshock infinite and shadow warrior

total instructions in shared programs : 1914931 -> 1903900 (-0.58%)
total gprs used in shared programs    : 247920 -> 247785 (-0.05%)
total local used in shared programs   : 5673 -> 5673 (0.00%)
total bytes used in shared programs   : 17558272 -> 17457320 (-0.57%)

                local        gpr       inst      bytes
    helped           0         137         719         719
      hurt           0          12           0           0

v2: remove this opt for OP_SLCT and check against float for OP_SET
v3: simplified the code

Signed-off-by: Karol Herbst <nouveau@karolherbst.de>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>