i965:use FRAMEBUFFER_UNSUPPORTED instead of FRAMEBUFFER_INCOMPLETE_DIMENSIONS

i965:use FRAMEBUFFER_UNSUPPORTED instead of FRAMEBUFFER_INCOMPLETE_DIMENSIONS

FRAMEBUFFER_INCOMPLETE_DIMENSIONS is not supported for GLES 3.0 and later and
not defined for Desktop OpenGL. Instead use FRAMEBUFFER_UNSUPPORTED like it
was done before.

Thanks to Iago Toral and Andrey Simiklit for pointing out the problem and the
details.

Fixes:  ebcde3454552adc6d3fea8af2207aafaba857796
   i965: be more specific about FBO completeness errors
Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>