microblaze: Add consistent code

Remove ancient Kconfig option for consistent code.
MMU uses cache inhibit pages.

noMMU uses UNCACHE SHADOW feature where is used double ram size.
For example:
Physical ram is 256MB and cache are setup to cover the same size.
But if you setup in HW that size is 512MB and cache covers 256MB
than you can use adresses from 256-512MB without caches and
correspond with 0-256MB with cache. That's why I am using
dcache base/high addresses to find out uncache area.

Signed-off-by: Michal Simek <monstr@monstr.eu>