This patch overrides the default weak definition of
`bl31_plat_runtime_setup()` for ARM Standard platforms to
specify a BL31 runtime console. ARM Standard platforms are
now expected to define `PLAT_ARM_BL31_RUN_UART_BASE` and
`PLAT_ARM_BL31_RUN_UART_CLK_IN_HZ` macros which is required
by `arm_bl31_plat_runtime_setup()` to initialize the runtime
console.

The system suspend resume helper `arm_system_pwr_domain_resume()`
is fixed to initialize the runtime console rather than the boot
console on resumption from system suspend.

Fixes ARM-software/tf-issues#220

Change-Id: I80eafe5b6adcfc7f1fdf8b99659aca1c64d96975