io: change inX() to have their own IO barrier overrides

Open code readX() inside inX() so that inX() variants have their own
overrideable Port IO barrier combinations as __io_pbr() and __io_par() for
actions to be taken before port IO and after port IO read.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>