net: enetc: fix implicit declaration of function FIELD_PREP

The kernel test robot reported the following error:

drivers/net/ethernet/freescale/enetc/ntmp.c: In function 'ntmp_fill_request_hdr':
drivers/net/ethernet/freescale/enetc/ntmp.c:203:38: error: implicit
declaration of function 'FIELD_PREP' [-Wimplicit-function-declaration]
203 |         cbd->req_hdr.access_method = FIELD_PREP(NTMP_ACCESS_METHOD,
    |                                      ^~~~~~~~~~

Therefore, add "bitfield.h" to ntmp_private.h to fix this issue.

Fixes: 4701073 ("net: enetc: add initial netc-lib driver to support NTMP")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Signed-off-by: Wei Fang <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Signed-off-by: NipaLocal <nipa@local>

Author: Wei Fang

drivers/net/ethernet/freescale/enetc/ntmp_private.h

@@ -7,6 +7,7 @@
 #ifndef __NTMP_PRIVATE_H
 #define __NTMP_PRIVATE_H
 
+#include <linux/bitfield.h>
 #include <linux/fsl/ntmp.h>
 
 #define NTMP_EID_REQ_LEN	8