Coccicheck: Remove memcpy to struct assignment test

The Coccinelle script scripts/coccinelle/misc/memcpy-assign.cocci look
for opportunities to replace a call to memcpy by a struct assignment.
This patch removes memcpy-assign.cocci as it is not clear that this
convention has an impact on the generated code.

Signed-off-by: Peter Senna Tschudin <[email protected]>
Signed-off-by: Michal Marek <[email protected]>