On GLES B8G8R8A8_SRGB is not available and B8G8R8A8_UNORM can not be
created as immutable. In order to have versions of these formats that
can be created immutable on GLES provide the formats R8G8B8A8_SRGB and
_UNORM with swizzling to BGRA that can then be used instead of the BGRA
formats. Since this may break things these swizzled versions will later
be only enabled when the guest requests them.

v2: Check the base swizzled BGRA format only on GL
v3: Correct type in method name (Gurchetan)
v4: Add PREFER_EMULATED_BRGA to according format binding flags (Gurchetan)
v5: Add comment about formats nou to be used in the guest (Gurchetan)

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>