package/dhcp: security bump to version 4.4.2-P1

package/dhcp: security bump to version 4.4.2-P1

Fixes the following security issue:

- CVE-2021-25217: A buffer overrun in lease file parsing code can be used to
  exploit a common vulnerability shared by dhcpd and dhclient

For details, see the advisory:
https://kb.isc.org/docs/cve-2021-25217

Update the LICENSE hash for a change of copyright years.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>