MN10300: Proper use of macros get_user() in the case of incremented pointers

Using __get_user_check(x, ptr++, size) leads to double increment of pointer.
This macro uses the macro get_user directly, which itself is used in this way
(get_user(x, ptr++)) in some functions of the kernel. The patch fixes the
error.

Reported-by: Tkhai Kirill <tkhai@yandex.ru>
Signed-off-by: David Howells <dhowells@redhat.com>