serial: Remove serial_putc_raw_dev

clang-3.8 reports that serial_putc_raw_dev in serial_ns16550.c is
unused.  Further investigation shows that we have 3 places that
implement this function and no callers, remove.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
3 files changed