i965: Add a weak no-op nir_print_instr() symbol

i965: Add a weak no-op nir_print_instr() symbol

intel_asm_annotation.c is part of libintel_compiler.la, which contains
code for disassembling and validating shaders that we want to call in
aubinator_error_decode.

dump_assembly() calls nir_print_instr() to print annotations, and
although dump_assembly() is not called by aubinator_error_decode (nor is
any function in intel_asm_annotation.c) it causes undefined references
to nir_print_instr().

To work around, provide a no-op weak symbol to resolve against.