pmb.install.partition: fix mb_reserved calculation
Calculate the end of the reserved space properly. Instead of:
from size_boot to size_reserve
it is:
from size_boot to (size_reserve + size_boot)
The reserved space is used by the on-device installer. Without this
patch, the reserved space could easily end up being too small, resulting
in no space left errors during the installation.
Should fix #2069 (closed), but I didn't verify that it works yet (hence Draft:).
Edited by Administrator