drivers/tty/hvc: Use strlcpy instead of strncpy

when strlen pi->location_code is larger than HVCS_CLC_LENGTH + 1,
    original implementation can not let hvcsd->p_location_code NUL terminated.
  so need fix it (also can simplify the code)

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>