Gallium: Add new CAPS to indicate whether a driver can switch SRGB write

Gallium: Add new CAPS to indicate whether a driver can switch SRGB write

Add a new cap that indicates whether the drivers supports
enabling/disabling the conversion from linear space to sRGB
for a framebuffer attachment. In Driver terms that this CAP indicates
whether the driver can switcht between a linear and and a sRGB surface
format for draw destinations witout changing the sourface itself.

v2: rename CAP to DEST_SURFACE_SRGB_CONTROL to reflect its
    purpouse better (pointed out by Ilia Mirkin)

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>