microblaze: Remove the buggy ALLOW_EDIT_AUTO config option

microblaze: Remove the buggy ALLOW_EDIT_AUTO config option

This was intended to allow manual override of CPU settings copied automatically
to Kconfig.auto, however it's problematic for several reasons, but mostly:

  * If the defconfig doesn't have ALLOW_EDIT_AUTO=y, then it's impossible for
    that defconfig to iverride the values in the kernel source tree.  This leads
    to very strange errors where the kernel is compiled with the wrong CPUFLAGS.

Next patch in the series will back out the default in Kconfig.auto to baseline
settings, so a kernel built with no default values will at least boot on any
hardware, just not make use of additional CPU features.

Signed-off-by: John Williams <john.williams@petalogix.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>