gallium/r600: Don't let h/w do endian swap for colorformat

gallium/r600: Don't let h/w do endian swap for colorformat

Since the rework on gallium pipe formats, there is no more need to do
endian swap of the colorformat in the h/w, because the conversion between
mesa format and gallium (pipe) format takes endianess into account (see
the big #if in p_format.h).

v2: return ENDIAN_NONE only for four 8-bits components
(V_0280A0_COLOR_8_8_8_8)

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Cc: "11.1 11.2" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>