asm-generic: generalize asm/sockios.h

ia64, parisc and sparc just use a copy of the generic version
of asm/sockios.h, and x86 is a redirect to the same file, so we
can just let the header file be generated.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>