Remove prints from VExpress NOR flash driver

There are way too many flash accesses for these prints to be useful.
As a result, they clobber the output (when they are enabled). They
might have been useful when the driver was developed but now that
it is more mature, their existence is arguable.

Change-Id: Ie068000ad2319c5f58f8bb7c7c891a24f6d21fdf
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>