r300: limit the number of available temporaries
Otherwise we overflow RC_REGISTER_MAX_INDEX and crash later. The overflow checking is already in place, however the array size did not take RC_REGISTER_MAX_INDEX into account so it was too big and the checks never triggered.
This is an alternate (and hopefully better) approach to the fix in !17383 (closed) .
Closes: #6017 (closed) Signed-off-by: Pavel Ondračka pavel.ondracka@gmail.com