isdn: use %pI4, remove get_{u8/u16/u32} and put_{u8/u16/u32} inlines

They would have been better named as get_be16, put_be16, etc.
as they were hiding an endian shift inside.

They don't add much over explicitly coding the byteshifting
and gcc sometimes has a problem with builtin_constant_p inside
inline functions, so it may do a better job of byteswapping
at compile time rather than runtime.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>