ARM: OMAP2+: omap_hwmod: Add support for earlycon

Hwmod core tries to reset and idles each IP that is registered with hwmod.
In case of earlycon, that specific uart IP cannot be reset or keep it in
idle state else earlycon hangs once hwmod resets that uart IP. So add support
to not reset uart that is being used as earlycon only if CONFIG_SERIAL_EARLYCON
is enabled.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>