tty: serial: msm_serial: Remove dead code

This config no longer exists now that mach-msm has been removed.
Delete it and the associated code.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: David Brown <davidb@codeaurora.org>
Cc: Bryan Huntsman <bryanh@codeaurora.org>
Cc: Daniel Walker <dwalker@fifo99.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>