serial: msm_geni_serial: Keep console enabled during shutdown

Currently the driver calls console_stop as a part of shutdown.
But we do not release the SE resources. It has been seen recently
that some userspace application might try to hangup the ttyMSM
terminal and that is leading to other apps/processes not able to
use the console for logging.

[ 25.985522] console_stop+0x10/0x18
[ 25.989124] msm_geni_serial_shutdown+0x34/0x148
[ 25.993877] uart_port_shutdown+0x40/0x54
[ 25.998007] uart_shutdown+0x94/0x168
[ 26.001781] uart_hangup+0x64/0x134
[ 26.005376] __tty_hangup+0x214/0x260
[ 26.009152] tty_vhangup+0x20/0x2c
[ 26.012663] tty_ioctl+0x190/0xaac
[ 26.016172] vfs_ioctl+0x3c/0x5c
[ 26.019503] do_vfs_ioctl+0x670/0x928
[ 26.023272] SyS_ioctl+0x90/0x9c
[ 26.026601] el0_svc_naked+0x34/0x38

Fix this by keeping the console enabled during shutdown.
This will enable other processes to keep using console.

Change-Id: Ia98c33089322326e991635b0172172b852f5fa4d
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>