arm: K3: Increase default SYSFW image size allocation

The memory allocated to store the FIT image containing SYSFW and board
configuration data is statically defined to the largest size expected.
This was 276000 bytes but now needs to be grown to 277000 to make room
for the slightly larger SYSFW image used on J721e High-Security devices.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>