i965/nir: Add OPT() and OPT_V() macros for invoking NIR passes.

i965/nir: Add OPT() and OPT_V() macros for invoking NIR passes.

OPT() is the normal macro for passes that return booleans, while OPT_V()
is a variant that works for passes that don't properly report progress.
(Such passes should be fixed to return a boolean, eventually.)

These macros take care of calling nir_validate_shader() and setting
progress appropriately.  In the future, it would be easy to add shader
dumping similar to INTEL_DEBUG=optimizer by extending the macro.

v2 (Jason Ekstrand):
 - Fix an unused variable warning

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>