ARM: versatile: name configuration options after actual board names

Update the option text to those which appear on the front of the
appropriate board user guides.  This gives consistent board naming, and
makes it obvious which option is for which platform.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>