msm: mhi: MHI Usperspace Control Interface driver

The MHI UCI driver exposes MHI core functionality to
userspace by means of device nodes.

The UCI driver exposes a device node for a pair of unidirectional
MHI channels.

The supported system calls on the device nodes are read, write,
select/poll and RS232 IOCTLs.

CRs-Fixed: 689329
Change-Id: Iceab97dba7c3bbb4eb7bf0c4ab0c1eac8c5417e9
Signed-off-by: Andrei Danaila <adanaila@codeaurora.org>