Makes write operation a parameter for tp_memcpy macro

Makes write operation a parameter for tp_memcpy macro

Memcpy source can be either user-space or kernel-space. To avoid code
duplication, this patch makes the operation a parameter to the macros.
Available macros are thus:

* tp_memcpy:               kernel-space array copy
* tp_memcpy_from_user:     user-space array copy
* tp_memcpy_dyn:           kernel-space sequence copy
* tp_memcpy_dyn_from_user: user-space sequence copy

Those are TP_fast_assign macros that can be used with __dynamic_array
macros in TP_STRUCT__entry in a TRACE_EVENT.

Signed-off-by: Francis Giraldeau <francis.giraldeau@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>