netfilter: nftables: add nft_parse_register_load() and use it

This new function combines the netlink register attribute parser
and the load validation function.

This update requires to replace:

	enum nft_registers      sreg:8;

in many of the expression private areas otherwise compiler complains
with:

	error: cannot take address of bit-field ‘sreg’

when passing the register field as reference.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -203,7 +203,7 @@ int nft_parse_u32_check(const struct nlattr *attr, int max, u32 *dest);
 unsigned int nft_parse_register(const struct nlattr *attr);
 int nft_dump_register(struct sk_buff *skb, unsigned int attr, unsigned int reg);
 
-int nft_validate_register_load(enum nft_registers reg, unsigned int len);
+int nft_parse_register_load(const struct nlattr *attr, u8 *sreg, u32 len);
 int nft_validate_register_store(const struct nft_ctx *ctx,
 				enum nft_registers reg,
 				const struct nft_data *data,

include/net/netfilter/nf_tables_core.h

@@ -26,14 +26,14 @@ void nf_tables_core_module_exit(void);
 struct nft_bitwise_fast_expr {
 	u32			mask;
 	u32			xor;
-	enum nft_registers	sreg:8;
+	u8			sreg;
 	enum nft_registers	dreg:8;
 };
 
 struct nft_cmp_fast_expr {
 	u32			data;
 	u32			mask;
-	enum nft_registers	sreg:8;
+	u8			sreg;
 	u8			len;
 	bool			inv;
 };
@@ -67,7 +67,7 @@ struct nft_payload_set {
 	enum nft_payload_bases	base:8;
 	u8			offset;
 	u8			len;
-	enum nft_registers	sreg:8;
+	u8			sreg;
 	u8			csum_type;
 	u8			csum_offset;
 	u8			csum_flags;

include/net/netfilter/nft_meta.h

@@ -8,7 +8,7 @@ struct nft_meta {
 	enum nft_meta_keys	key:8;
 	union {
 		enum nft_registers	dreg:8;
-		enum nft_registers	sreg:8;
+		u8		sreg;
 	};
 };