egl: Fix the bad surface attributes combination checking for pbuffers. (v3)

egl: Fix the bad surface attributes combination checking for pbuffers. (v3)

Fixes a regression induced by commit a0674ce5c41903ccd161e89abb149621bfbc40d2:
When EGL_TEXTURE_FORMAT and EGL_TEXTURE_TARGET were both specified (and
both != EGL_NO_TEXTURE), an error was instantly triggered, before the
other one had even a chance to be checked, which is obviously not the
intended behaviour.

v2: Full commit hash, remove useless variables.
v3: [chadv] Add Fixes footers.

Fixes: piglit "spec/egl 1.4/eglcreatepbuffersurface and then glclear"
Fixes: piglit "spec/egl 1.4/largest possible eglcreatepbuffersurface and then glclear"
Signed-off-by: Guillaume Charifi <guillaume.charifi@sfr.fr>
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Reviewed-by: Chad Versace <chad.versace@intel.com>