ARM: s3c24xx: simplify mach/io.h

s3c24xx has a custom implementation of the inb/outb family of I/O
accessors, implementing both general register access and ISA I/O port
through a multiplexer.

As far as I can tell, the first case has never been needed, and certainly
is not used now, as drivers only use inb/outb to actually driver ISA or
PCI port I/O.

Similarly, the special ISA support is limited to a single machine, the
Simtec Electronics BAST (EB2410ITX) with its PC/104 expansion connector,
all other machines could simply use the generic implementation from
asm/io.h that expects a single memory-mapped address range for byte,
word and dword access. As no other machines besides BAST actually selects
CONFIG_ISA, this is likely not even necessary.

As a cleanup, remove support for the non-ISA access from the helpers,
and make the ISA access use the virtual address window that we use
elsewhere for PCI I/O ports. In configurations without the BAST machine,
this now falls back on the generic implementation from asm/io.h, but
the mach/io.h header is still relied on to include a number of other
header files implicitly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200806182059.2431-7-krzk@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>