fm10k: Resolve compile warnings with W=1

Fix two cases where variables are being set but not used.

Signed-off-by: Matthew Vick <matthew.vick@intel.com>
Tested-by: Krishneil Singh<Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c b/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c
index 14a4ea7..9f5457c 100644
--- a/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_mbx.c
@@ -1194,12 +1194,11 @@
 {
 	const enum fm10k_mbx_state state = mbx->state;
 	const u32 *hdr = &mbx->mbx_hdr;
-	u16 head, tail;
+	u16 head;
 	s32 err;
 
-	/* we will need to pull all of the fields for verification */
+	/* we will need to pull the header field for verification */
 	head = FM10K_MSG_HDR_FIELD_GET(*hdr, HEAD);
-	tail = FM10K_MSG_HDR_FIELD_GET(*hdr, TAIL);
 
 	/* We should not be receiving disconnect if Rx is incomplete */
 	if (mbx->pushed)