msm_serial: Send more than 1 character on the console w/ UARTDM

We recently added support to send more than one character at a
time for UARTDM hardware but we didn't add the same support in
the console code path. Add support here to speed up console
messages on UARTDM hardware.

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