Despite the switch to right UART driver (prev patch), serial console
still doesn't work due to missing CONFIG_SERIAL_OF_PLATFORM

Also fix the default cmdline in DT to not refer to out-of-tree
ARC framebuffer driver for console.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: <stable@vger.kernel.org>   #3.10, 3.12, 3.13, 3.14
Cc: Francois Bedard <Francois.Bedard@synopsys.com>