sh: eliminate unused irq_reg_{readl,writel} accessors

Defining these macros way down in arch/sh/.../irq.c doesn't cause
kernel/irq/generic-chip.c to use them.  As far as I can tell this code has
no effect.

Fixes: 332fd7c4 ("genirq: Generic chip: Change irq_reg_{readl,writel} arguments")
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> (cpp/asm comparison)
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>