openrisc: Cleanup emergency print handling

openrisc: Cleanup emergency print handling

The emergency print support only works for 8250 compatible serial ports.
Now that OpenRISC platforms may be configured with different serial port
hardware we don't want emergency print to try to print to non-existent
hardware which will cause lockups.

This patch contains several fixes to get emergency print working again:

 - Update symbol loading to not assume the location of symbols
 - Split the putc print operation out to its own function to allow
   for different future implementations.
 - Update _emergency_print_nr and _emergency_print to use the putc
   function.
 - Guard serial 8250 specific sequences by CONFIG_SERIAL_8250
 - Update string line feed from lf,cr to cr,lf.

Signed-off-by: Stafford Horne <shorne@gmail.com>