[ARM] 3118/1: fix and reenable nwfpe extended precision emulation for big-endian

Patch from Lennert Buytenhek

nwfpe extended precision emulation used to be broken on big-endian
and was therefore disabled.  This patch fixes nwfpe so that it copies
extended precision floats to/from userspace in the proper word order
(similar to patch #2046, see the description of that patch for an
explanation) and reenables the Kconfig option.

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>