[PATCH] free e820 reserved memory in bootargs memmap

[zoucao]

add a new chareater "-" in bootargs memmap, you can use this chareater to free
e820 reserved memory, for example:

reserved iomem:
	cat /proc/iomem:
	......
	00100000-6aefefff : System RAM
	  01000000-0165537a : Kernel code
	  0165537b-01a8873f : Kernel data
	  01c31000-01f4efff : Kernel bss
	  28000000-320fffff : Crash kernel
	6aeff000-6effffff : reserved       --> it is e820 reserved memory
	6f000000-78240fff : System RAM
	......


add bootargs memmap=0x4101000-0x6aeff000, to free memory region: 6aeff000-6effffff
then 6aeff000-6effffff will be merged into 00100000-78240fff.

new iomem:  
	cat /proc/iomem:
	......
	00100000-78240fff : System RAM
	  01000000-0165537a : Kernel code
	  0165537b-01a8873f : Kernel data
	  01c31000-01f4efff : Kernel bss
	......