powerpc/ps3: Workaround for flash memory I/O error

A workaround for flash memory I/O errors when the PS3 internal
hard disk has not been formatted for OtherOS use.

This error condition mainly effects 'Live CD' users who have not
formatted the PS3's internal hard disk for OtherOS.

Fixes errors similar to these when using the ps3-flash-util
or ps3-boot-game-os programs:

  ps3flash read failed 0x2050000
  os_area_header_read: read error: os_area_header: Input/output error
  main:627: os_area_read_hp error.
  ERROR: can't change boot flag

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>