net/sfc/base: fix build because of no declaration

Functions declared in mcdi_mon.h are implemented in mcdi_mon.c.
The build fails if compiler options require declaration before definition.

Fixes: dfb3b1ce15 ("net/sfc/base: import monitors access via MCDI")
Cc: stable@dpdk.org

Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>

drivers/net/sfc/base/mcdi_mon.c

@@ -6,6 +6,7 @@
 
 #include "efx.h"
 #include "efx_impl.h"
+#include "mcdi_mon.h"
 
 #if EFSYS_OPT_MON_MCDI