Use the BL3-1 runtime console as the crash console.

This patch reassigns the crash console on Juno and FVP to use the runtime
BL3-1 console. The crash console is changed to SoC UART0 (UART2) from the
previous FPGA UART0 (UART0) on Juno. In FVP, it is changed from UART0 to
UART1.

Fixes ARM-software/tf-issues#256

Change-Id: I7df54f86ca00ec2652c27261dd66a94c12610816