nv50/ir: move LateAlgebraicOpt to the very end

nv50/ir: move LateAlgebraicOpt to the very end

Memory loads can take offsets, but the SHLADD will often attempt to
consume the offsets too. As there may be multiple memory loads with the
same base but different offsets, those would end up in a SHLADD instead
of the offset of the memory operation.

This moves the pass after we've had a chance to attempt to propagate
immediate adds into the indirect offset.

total instructions in shared programs : 6580681 -> 6567716 (-0.20%)
total gprs used in shared programs    : 944261 -> 943375 (-0.09%)
total shared used in shared programs  : 0 -> 0 (0.00%)
total local used in shared programs   : 15328 -> 15328 (0.00%)
total bytes used in shared programs   : 60339896 -> 60221504 (-0.20%)

                local     shared        gpr       inst      bytes
    helped           0           0         555        2698        2698
      hurt           0           0         138         336         336

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>