ARM: fixmap early permanent mapping support

This adds early permanent mapping support to fixmap early mappings.
Unlike early_ioremap mappings, permanent mappings are kept after
paging_init. Each permament mapping must be explicitly added.
Initially, the only permanent mapping is for early console.

The early pmd and ptes are still destroyed and recreated since the
attributes may change as the memory types are initialized

Change-Id: I49b2adfe6f25be3a40324883c6862c99185f027a
Cc: Mark Salter <msalter@redhat.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Rob Herring <robh@kernel.org>
Git-commit: d0e6f4365fab9b8505ca97955e9769132c10aaf4
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git


[vabbar@codeaurora.org: Fixed trivial merge conflicts]
Signed-off-by: Venkatesh Yadav Abbarapu <vabbar@codeaurora.org>