serial: samsung: Neaten dbg uses

Add format and argument checking and fix misuses in the dbg macro.

Add __printf
Use %pR for resource
Add #include guard to samsung.h
Move static functions from .h to .c
Use vscnprintf instead of length unguarded vsprintf

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>