[ARM] 3756/1: Assign value for HWCAP_IWMMXT

Patch from Paul Gortmaker

Some folks here at Wind River asked me if I'd push this out
so that the value was generally agreed upon in advance by
all folks interested in working with iWMMXt.  Seems simple
enough...

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>