Fix the function conflict in x86emu when DEBUG is on

The function parse_line() in common/main.c was exposed globally by commit
6636b62a, Result in conflict with the same
name funciton in drivers/bios_emulator/x86emu/debug.c when define the DEBUG.
This patch fix this by renaming the function in the debug.c file.

Signed-off-by: Jason Jin <Jason.jin@freescale.com>