omap4-common: fix permission for sdcard0 and mark sdcards nonemulated

This change fixes applications on sd-card vanishing on reboot due to
sdcard0 being mounted as root (as /ss is mounted as root) and
both sdcards not being marked as nonemulated.

Change-Id: I766a4bbd9de1b62c9a0c9efa1db1618911b58e6b
omap4-common: /ss does not need to be world read-/writable

Change-Id: I6a9fd9e95b9b8f813961eb2c5704cf65b11a7426