netfilter: nft_payload: extend offset to 65535 bytes

netfilter: nft_payload: extend offset to 65535 bytes

In some situations 255 bytes offset is not enough to match or manipulate
the desired packet field. Increase the offset limit to 65535 or U16_MAX.

In addition, the nla policy maximum value is not set anymore as it is
limited to s16. Instead, the maximum value is checked during the payload
expression initialization function.

Tested with the nft command line tool.

table ip filter {
	chain output {
		@nh,2040,8 set 0xff
		@nh,524280,8 set 0xff
		@nh,524280,8 0xff
		@nh,2040,8 0xff
	}
}

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Florian Westphal <fw@strlen.de>