glsl: cleanup and fix validate matrix function for arrays
glsl: cleanup and fix validate matrix function for arrays

Previously if the member was an array of matrices then a
warning message would be incorrectly given.

Also the struct case could never be met so it has been removed.

Reviewed-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler