glsl: correctly validate component layout qualifier for dvec{3,4}

glsl: correctly validate component layout qualifier for dvec{3,4}

From page 62 (page 68 of the PDF) of the GLSL 4.50 v.7 spec:

  " A dvec3 or dvec4 can only be declared without specifying a
    component."

Therefore, using the "component" qualifier with a dvec3 or dvec4
should result in a compiling error.

v2: enhance the error message (Timothy).

Fixes: 94438578d21 ("glsl: validate and store component layout qualifier in GLSL IR")
Cc: Timothy Arceri <tarceri@itsqueeze.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>