msm: smd_tty: Support multiplatform

Upstream prefers existing drivers be converted to support multiplatform
kernels.  This requires drivers to be located in generic functionality
directories instead of specific mach directories.

Move the smd_tty driver to the drivers/tty/serial location to support
multiplatform.

Change-Id: Ia5cb5f98ca07817900470252b21e47622bf23ee9
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>