fix(n1sdp): mapping Run-time UART to IOFPGA UART0

Currently the Run-time UART is mapped to AP UART1 which is internally
routed to MCP UART1, so unsharing it from AP UART1 and mapping it to
IOFPGA UART0 for exclusiveness among the usage of the UARTs.

Signed-off-by: Himanshu Sharma <Himanshu.Sharma@arm.com>
Change-Id: I366740a971a880decf0d373e9055e7ebda5df53a