drm: tidss: Fix pixel format definition

drm: tidss: Fix pixel format definition

There was a long-standing bug from a typo that created 2 ARGB1555 and
ABGR1555 pixel format entries. Weston 10 has a sanity check that alerted
me to this issue.

According to the Supported Pixel Data formats table we have the later
entries should have been for Alpha-X instead.

Signed-off-by: Randolph Sapp <rs@ti.com>
Fixes: 32a1795f57eecc ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
Reviewed-by: Aradhya Bhatia <a-bhatia1@ti.com>
Acked-by: Andrew Davis <afd@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221202001803.1765805-1-rs@ti.com