uapi: fix big endian definition of ipv6_rpl_sr_hdr

Following RFC 6554 [1], the current order of fields is wrong for big
endian definition. Indeed, here is how the header looks like:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Next Header  |  Hdr Ext Len  | Routing Type  | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CmprI | CmprE |  Pad  |               Reserved                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

This patch reorders fields so that big endian definition is now correct.

  [1] https://tools.ietf.org/html/rfc6554#section-3

Fixes: cfa933d9 ("include: uapi: linux: add rpl sr header definition")
Signed-off-by: Justin Iurman <justin.iurman@uliege.be>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/uapi/linux/rpl.h

@@ -28,10 +28,10 @@ struct ipv6_rpl_sr_hdr {
 		pad:4,
 		reserved1:16;
 #elif defined(__BIG_ENDIAN_BITFIELD)
-	__u32	reserved:20,
+	__u32	cmpri:4,
+		cmpre:4,
 		pad:4,
-		cmpri:4,
-		cmpre:4;
+		reserved:20;
 #else
 #error  "Please fix <asm/byteorder.h>"
 #endif