glsl: free hash tables earlier
glsl: free hash tables earlier

These are only used by get_matching_input() which has been call
at this point so free the hash tables.

Reviewed-by: Iago Toral Quiroga <a847aabaac44184372f6b1cd1a59aa254daaeb0b@igalia.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler