libcacard: replace pstrcpy() with memcpy()

libcacard: replace pstrcpy() with memcpy()

Commit 2e679780ae86c6ca8 replaced strncpy() with pstrcpy()
in one place in libcacard.  This is a qemu-specific function,
while libcacard is a stand-alone library (or tries to be).
But since we know the exact length of the string to copy,
and know that it definitely will fit in the destination
buffer, use memcpy() instead, and null-terminate the string
after that.

An alternative is to use g_strlcpy() or strncpy(), but memcpy()
is more than adequate in this place.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: qemu-trivial@nongnu.org
Cc: Alon Levy <alevy@redhat.com>