libpayload: Cache copy of cb_framebuffer struct

Our AArch64 code supports dynamic framebuffer allocation which
makes it necessary to change the framebuffer information during
runtime. Having a pointer inside `libsysinfo` made a mess of it
as the pointer would either refer to the original struct inside
the coreboot table or to a new struct inside payload space. The
latter would be unaffected by a relocation of the payload.

Instead of the pointer, we'll always keep a copy of the whole
struct, which can be altered on demand without affecting the
coreboot table. To align the `video/graphics` driver with the
console driver, we also replace `fbaddr` with a macro `FB` that
calls phys_to_virt().

Change-Id: I3edc09cdb502a71516c1ee71457c1f8dcd01c119
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43578
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

payloads/libpayload/include/sysinfo.h

@@ -81,7 +81,7 @@ struct sysinfo_t {
 
 	char *cb_version;
 
-	struct cb_framebuffer *framebuffer;
+	struct cb_framebuffer framebuffer;
 
 	int num_gpios;
 	struct cb_gpio gpios[SYSINFO_MAX_GPIOS];