drm/gma500: Use gma_ prefix for our i2c abstraction

psb_intel_i2c_chan is used by all chips so use the correct prefix.

Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220601092311.22648-2-patrik.r.jakobsson@gmail.com