dri: Choose a decent global driNConfigOptions.

dri: Choose a decent global driNConfigOptions.

Previously, we were asserting that each driver specified an NConfigOptions
exactly equal to the number of options they supplied, leading to frequent
bugs when people would forget to adjust the value when adjusting driver
options.  Instead, just overallocate the table by a bit and leave sanity
checking to the assert in findOption().

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>