mesa/main: Fix GetTextureImage error reporting

mesa/main: Fix GetTextureImage error reporting

GetTex*Image should return INVALID_ENUM if target is not valid, however,
GetTextureImage does not receive a target, and instead should return
INVALID_OPERATION if the effective target is not valid. From the
OpenGL 4.6 core profile spec, section 8.11 Texture Queries:

"An INVALID_OPERATION error is generated by GetTextureImage if the effective
 target is not one of TEXTURE_1D, TEXTURE_2D, TEXTURE_3D, TEXTURE_1D_ARRAY,
 TEXTURE_2D_ARRAY, TEXTURE_CUBE_MAP_ARRAY, TEXTURE_RECTANGLE, or
 TEXTURE_CUBE_MAP (for GetTextureImage only)."

Fixes:
KHR-GL45.direct_state_access.textures_image_query_errors

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>