byteorder: use generic C version for value byteswapping

This makes the new implementation of the byteorder helpers match the old
in how it degraded when an arch-defined version was not available:

1) swab()
- look for arch defined
- if not, use generic c version

2) swabp()
- look for arch-defined
- if not, deref pointer and use swab()

3) swabs()
- look for arch defined
- if not, use swabp

Signed-off-by: Harvey Harrison <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/swab.h

···
 {
 #ifdef __arch_swab16
 	return __arch_swab16(val);
-#elif defined(__arch_swab16p)
-	return __arch_swab16p(&val);
 #else
 	return __const_swab16(val);
 #endif
···
 {
 #ifdef __arch_swab32
 	return __arch_swab32(val);
-#elif defined(__arch_swab32p)
-	return __arch_swab32p(&val);
 #else
 	return __const_swab32(val);
 #endif
···
 {
 #ifdef __arch_swab64
 	return __arch_swab64(val);
-#elif defined(__arch_swab64p)
-	return __arch_swab64p(&val);
 #elif defined(__SWAB_64_THRU_32__)
 	__u32 h = val >> 32;
 	__u32 l = val & ((1ULL << 32) - 1);
···
 {
 #ifdef __arch_swahw32
 	return __arch_swahw32(val);
-#elif defined(__arch_swahw32p)
-	return __arch_swahw32p(&val);
 #else
 	return __const_swahw32(val);
 #endif
···
 {
 #ifdef __arch_swahb32
 	return __arch_swahb32(val);
-#elif defined(__arch_swahb32p)
-	return __arch_swahb32p(&val);
 #else
 	return __const_swahb32(val);
 #endif