i965: Don't use GCC extension for ?: with only two operands.

i965: Don't use GCC extension for ?: with only two operands.

From the "apparently I don't know C" files...GCC apparently supports:

    x ?: y

which is equivalent to

    x ? x : y

except that it doesn't cause side-effects to occur twice.  See:
https://gcc.gnu.org/onlinedocs/gcc/Conditionals.html#Conditionals

This was confusing and looked like a typo.  It doesn't really buy us
anything, so just write the obvious code in normal C.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>