Prior to this commit, we don't consider the offset of the irom vaddr
start.
If the offset + size is bigger than the MMU page size, for example:
MMU page size: 0x10000
irom vaddr: 0x4200_0800, so offset = 0x800
irom size: 0xF900
offset + size = 0x10100
Under this condition, the 0x4200_0000 ~ 0x4202_0000, two MMU pages are
used.
With this commit, when reserving the irom and drom, we take the offset
into consideration as well.
