Presently the SH7720/21 serial code uses asm/gpio.h to get at the CPU
GPIO port definitions, but in the case of GPIOLIB=y this also includes
references to generic GPIOLIB routines that we don't have any function
declarations for, tripping up on -Werror=implicit-function-declaration
with newer gcc versions:

  CC      arch/sh/kernel/cpu/sh3/serial-sh7720.o
In file included from include/linux/sh_pfc.h:14:0,
                 from arch/sh/include/asm/gpio.h:23,
                 from arch/sh/kernel/cpu/sh3/serial-sh7720.c:5:
include/asm-generic/gpio.h: In function 'gpio_get_value_cansleep':
include/asm-generic/gpio.h:220:2: error: implicit declaration of function '__gpio_get_value' [-Werror=implicit-function-declaration]
include/asm-generic/gpio.h: In function 'gpio_set_value_cansleep':
include/asm-generic/gpio.h:226:2: error: implicit declaration of function '__gpio_set_value' [-Werror=implicit-function-declaration]
In file included from arch/sh/include/asm/gpio.h:23:0,
                 from arch/sh/kernel/cpu/sh3/serial-sh7720.c:5:
include/linux/sh_pfc.h: At top level:
include/linux/sh_pfc.h:121:19: error: field 'chip' has incomplete type

Switch to using the cpu/ version for the port definitions explicitly.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

This fixes up build issues for SH7720/SH7722/SH7750 that crept in with
the serial rework.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

This takes a bit of a sledgehammer to the horribly CPU subtype
ifdef-ridden header and abstracts all of the different register layouts
in to distinct types which in turn can be overriden on a per-port basis,
or permitted to default to the map matching the port type at probe time.

In the process this ultimately fixes up inumerable bugs with mismatches
on various CPU types (particularly the legacy ones that were obviously
broken years ago and no one noticed) and provides a more tightly coupled
and consolidated platform for extending and implementing generic
features.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>