boot: boot_serial: Add updated SMP header

Adds missing fields which were wrongly treated as part of the
operation value, which they were not, and adds a big/little
endian check.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

boot/boot_serial/src/boot_serial_priv.h

@@ -60,7 +60,15 @@ extern "C" {
 #endif
 
 struct nmgr_hdr {
- uint8_t nh_op; /* NMGR_OP_XXX */
+#if (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+ uint8_t _res1:3;
+ uint8_t nh_version:2;
+ uint8_t nh_op:3; /* NMGR_OP_XXX */
+#else
+ uint8_t nh_op:3; /* NMGR_OP_XXX */
+ uint8_t nh_version:2;
+ uint8_t _res1:3;
+#endif
  uint8_t nh_flags;
  uint16_t nh_len; /* length of the payload */
  uint16_t nh_group; /* NMGR_GROUP_XXX */