Prevent wiping /misc when entering recovery

Some old bootloader code wipes /misc upon entering recovery. These HTC
devices don't do anything funny like the old days where /misc had
commands embedded to wipe data or call recovery, so we don't need to
wipe all or part of the partition. On the other hand, /misc does hold
some values read by HBOOT, including the OS version, so it's actually
a good idea to make sure it's not touched. This is a simple matter of
not telling recovery where /misc is located.