glsl/linker: Make several functions not static

glsl/linker: Make several functions not static

copy_constant_to_storage, set_uniform_initializer,
populate_consumer_input_sets, and get_matching_input are all used by
tests in src/compiler/glsl/tests:

glsl/tests/varyings_test.o: In function `link_varyings_single_simple_input_Test::TestBody()':
src/compiler/glsl/tests/varyings_test.cpp:131: undefined reference to `linker::populate_consumer_input_sets(void*, exec_list*, hash_table*, hash_table*, ir_variable**)'
glsl/tests/varyings_test.o: In function `link_varyings_gl_ClipDistance_Test::TestBody()':
src/compiler/glsl/tests/varyings_test.cpp:159: undefined reference to `linker::populate_consumer_input_sets(void*, exec_list*, hash_table*, hash_table*, ir_variable**)'
glsl/tests/varyings_test.o: In function `link_varyings_gl_CullDistance_Test::TestBody()':
src/compiler/glsl/tests/varyings_test.cpp:186: undefined reference to `linker::populate_consumer_input_sets(void*, exec_list*, hash_table*, hash_table*, ir_variable**)'
glsl/tests/varyings_test.o: In function `link_varyings_single_interface_input_Test::TestBody()':
src/compiler/glsl/tests/varyings_test.cpp:208: undefined reference to `linker::populate_consumer_input_sets(void*, exec_list*, hash_table*, hash_table*, ir_variable**)'
glsl/tests/varyings_test.o: In function `link_varyings_one_interface_and_one_simple_input_Test::TestBody()':
src/compiler/glsl/tests/varyings_test.cpp:241: undefined reference to `linker::populate_consumer_input_sets(void*, exec_list*, hash_table*, hash_table*, ir_variable**)'
glsl/tests/varyings_test.o:src/compiler/glsl/tests/varyings_test.cpp:272: more undefined references to `linker::populate_consumer_input_sets(void*, exec_list*, hash_table*, hash_table*, ir_variable**)' follow
glsl/tests/varyings_test.o: In function `link_varyings_interface_field_doesnt_match_noninterface_Test::TestBody()':
src/compiler/glsl/tests/varyings_test.cpp:289: undefined reference to `linker::get_matching_input(void*, ir_variable const*, hash_table*, hash_table*, ir_variable**)'
glsl/tests/varyings_test.o: In function `link_varyings_interface_field_doesnt_match_noninterface_vice_versa_Test::TestBody()':
src/compiler/glsl/tests/varyings_test.cpp:314: undefined reference to `linker::populate_consumer_input_sets(void*, exec_list*, hash_table*, hash_table*, ir_variable**)'
src/compiler/glsl/tests/varyings_test.cpp:328: undefined reference to `linker::get_matching_input(void*, ir_variable const*, hash_table*, hash_table*, ir_variable**)'

Fixes: ca73c3358c91 ("glsl: Mark functions static")
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>