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
......
