Increase the maximum number of disk partitions to 8

Linaro's tools create images with more than 4 partitions, so this change
is needed so vold sees these extra partitions, like the sdcard
partition.

MAX_PARTS is also deleted because it's not used and to avoid ambiguity.

Change-Id: Ia67f672d3b343b55b8354a09a1d17dd00679cd6f
Allow symlinks to be used in vold.fstab

With device-tree kernels the sysfs path for SD cards varies
depending on device-tree layout and the actual card used. It is
therefore impossible to specify the sysfs path for the device
in vold.fstab.

However, there exists a symlink to the device which is created under a
generic path like '/sys/block/mmcblk0/device'. To use such a path with
vold we need to convert the symlinked path to the real path, which this
patch does.

Change-Id: Ifc810593a8fa390f875762eecd5c3413e62c1d16
Signed-off-by: Jon Medhurst <tixy@linaro.org>
vold: Handle wrong entries in vold.fstab

If the entry in vold.fstab doesn't exist then vold
is crashing in realpath where it tries to resolve
symlink.

Due to the crash in vold the system keeps restarting
vold and never completes the boot process.

This fixes the bugs:
https://bugs.launchpad.net/linaro-android/+bug/1048476
https://bugs.launchpad.net/linaro-android/+bug/1047964

Change-Id: I49a2da8c8813afcbf0dbaede6bc19dc987db61a6
Signed-off-by: Vishal Bhoj <vishal.bhoj@linaro.org>