tty: serial: msm: Support big-endian CPUs

To support big-endian CPUs use the string versions of the io
read/write macros on the TX/RX fifos and the non-raw variants of
the readl/writel macros throughout. This way we don't byteswap
the characters coming from the fifos but we properly deal with
the little-endian nature of the serial hardware while controlling
it.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>