sh: Fix CONFIG_PMB=n build.

The last commit introduced the following breakage

arch/sh/include/asm/mmu.h: In function 'pmb_remap':
arch/sh/include/asm/mmu.h:79: error: expected ';' before '}' token

and...

arch/sh/include/asm/mmu.h:78: error: 'EINVAL' undeclared (first use in this function)
arch/sh/include/asm/mmu.h:78: error: (Each undeclared identifier is reported only once
arch/sh/include/asm/mmu.h:78: error: for each function it appears in.)
arch/sh/include/asm/mmu.h: In function 'pmb_init':
arch/sh/include/asm/mmu.h:87: error: 'ENODEV' undeclared (first use in this function)

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>