sparc: fix warnings in userspace header byteorder.h

Fix following warnings in byteorder.h:

byteorder.h:4: include of <linux/types.h> is preferred over <asm/types.h>
byteorder.h:9: leaks CONFIG_SPARC32 to userspace where it is not valid
byteorder.h:13: leaks CONFIG_SPARC64 to userspace where it is not valid
byteorder.h:14: found __[us]{8,16,32,64} type without #include <linux/types.h>
byteorder.h:47: leaks CONFIG_SPARC64 to userspace where it is not valid

- changed to use include <linux/types.h> as suggested
- use preprocessor defined symbols to distingush between 32 and 64 bit

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>