ARM: 8085/1: sa1100: collie: add top boot mtd partition

The CFI mapping is now perfect so we can expose the top block, read only.
There isn't much to read, though, just the sharpsl_params values.

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>