gm200/ir: optimize rcp(sqrt) to rsq

gm200/ir: optimize rcp(sqrt) to rsq

mitigates hurt shaders after adding sqrt:
total instructions in shared programs : 5456166 -> 5454825 (-0.02%)
total gprs used in shared programs    : 647522 -> 647551 (0.00%)
total shared used in shared programs  : 389120 -> 389120 (0.00%)
total local used in shared programs   : 21064 -> 21064 (0.00%)
total bytes used in shared programs   : 58288696 -> 58274448 (-0.02%)

                local     shared        gpr       inst      bytes
    helped           0           0           0         516         516
      hurt           0           0          27           2           2

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Karol Herbst <kherbst@redhat.com>