microblaze: Remove generic platform

All microblaze platforms are using the same configuration
that's why there is no reason to use generic platform.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

diff --cc arch/microblaze/platform/Kconfig.platform
Simple merge

diff --cc arch/microblaze/platform/Makefile
Simple merge

diff --cc arch/microblaze/platform/generic/Kconfig.auto
Simple merge

diff --cc arch/microblaze/platform/generic/Makefile
Simple merge