ext4: use memcpy() instead of strcpy()

ext4: use memcpy() instead of strcpy()

The strcpy() function is considered dangerous and eeeevil by people
who are using sophisticated code analysis tools such as "grep".  This
is true even when a quick inspection would show that the source is a
constant string ("." or "..") and the destination is a fixed array
which is guaranteed to have enough space.  Make the "grep" code
analysis tool happy by using memcpy() isstead of strcpy().  :-)

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://patch.msgid.link/20250712181249.434530-2-tytso@mit.edu
Signed-off-by: Theodore Ts'o <tytso@mit.edu>