sh: sh7734: Correct SCIF type for BRG

The SCIF variant in the sh7734 SoC is not the common "SH-4(A)" variant,
but a derivative with added "Baud Rate Generator for External Clock"
(BRG). Correct the regtype value in platform data to fix this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>