nir: Silence unused parameter warnings

nir: Silence unused parameter warnings

In file included from src/compiler/nir/nir_opt_algebraic.c:4:0:
src/compiler/nir/nir_search_helpers.h: In function ‘is_not_const’:
src/compiler/nir/nir_search_helpers.h:118:59: warning: unused parameter
‘num_components’ [-Wunused-parameter]
 is_not_const(nir_alu_instr *instr, unsigned src, unsigned num_components,
                                                           ^~~~~~~~~~~~~~
src/compiler/nir/nir_search_helpers.h:119:29: warning: unused parameter
‘swizzle ’ [-Wunused-parameter]
              const uint8_t *swizzle)
                             ^~~~~~~

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>