ARM: dts: r8a7793: Adjust SMP routine size

This patch adjusts the definition of the SMP routine size according
to the latest changes made by commit:
"ARM: shmobile: Add watchdog support"

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>