drm/gma500: Remove unused i8xx clock limits

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
drm/gma500: Calculate clock in one function instead of three identical

i9xx_clock() and i8xx_clock() did the same calc and psb_intel_clock() just
called i9xx_clock() so just move it all into psb_intel_clock().

The same calculation is duplicated in cdv_intel_display.c as well so maybe we
can share it later on.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
drm/gma500: Type clock limits directly into array and remove defines

This makes it easier to read. We do the same for cdv so it becomes more
consistent as well.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
drm/gma500: Remove unnecessary function exposure

psb_intel_crtc_gamma_set() and psb_intel_crtc_destroy() aren't used outside of
psb_intel_display.c right now so no need to expose them.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
drm/gma500: Clean up various defines

Remove unused defines that we'll never use and fix naming in some include guards

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>