protobuf: replace the constant 4294967295 with 0xFFFFFFFF in generated sources

This workarounds a compilation warning on ARM:

	packet-sock.pb-c.c: In function 'packet_sock_entry__init':
	packet-sock.pb-c.c:98:3: error: this decimal constant is unsigned only in ISO C90 [-Werror]
	packet-sock.pb-c.c: At top level:
	packet-sock.pb-c.c:318:1: error: this decimal constant is unsigned only in ISO C90 [-Werror]

Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>