r600g: LIT: swap MUL_LIT operands to fix 0^0

r600g: LIT: swap MUL_LIT operands to fix 0^0

For 0^0 case result of "LOG_CLAMPED ...,0" is -MAX_FLOAT, and then result of
"MUL_LIT ...,0,-MAX_FLOAT,..." is -MAX_FLOAT instead of 0 because of special
src1 checks for -MAX_FLOAT. So swap src0/1:
"MUL_LIT ...,-MAX_FLOAT,0,..." to get expected 0, then result of
"EXP_IEEE ...,0" is 1 as expected for LIT.

Signed-off-by: Vadim Girlin <vadimgirlin@gmail.com>