sh64: Move *_p() I/O routine variants to io.h.

These were implemented using an ugly macro for just simple wrapping,
so we just make the wrapping explicit and move it to io.h instead.

Also fixes up some modules:

  CC [M]  drivers/net/8390.o
  In file included from drivers/net/8390.c:6:
  drivers/net/lib8390.c: In function 'ei_start_xmit':
  drivers/net/lib8390.c:329: error: implicit declaration of function 'outb_p'
  drivers/net/lib8390.c: In function '__ei_interrupt':
  drivers/net/lib8390.c:457: error: implicit declaration of function 'inb_p'
  make[2]: *** [drivers/net/8390.o] Error 1
  make[1]: *** [drivers/net] Error 2

Signed-off-by: Paul Mundt <lethal@linux-sh.org>