x86: correctly wire up the newuname system call

x86: correctly wire up the newuname system call

Before commit b6ede17dffa36ba28e67ba723ecc335f57baa86b ("improve
sys_newuname() for compat architectures") 64-bit x86 had a private
implementation of sys_uname which was just called sys_uname, which other
architectures used for the old uname.

Due to some merge issues with the uname refactoring patches we ended up
calling the old uname version for both the old and new system call
slots, which lead to the domainname filed never be set which caused
failures with libnss_nis.

Reported-and-tested-by: Andy Isaacson <adi@hexapodia.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>