NVRAM access may be needed early in boot process. Reading it using mtd
happens quite late in the init process. Add NVRAM initialization to the
NVMEM driver which comes up early and depends on IO mapping only.
This is required by Linksys devices which use NVRAM content for proper
partitioning (detecting current firmware partition).
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit baf04eed02)
