pld: validate exported functions by including its own .h

Let source files to include its file .h to validate the exported
prototypes.

Detected through 'sparse' tool.

Change-Id: I217c2903fdb19e1a2cce39d2536a903c3d72f3f7
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7664
Tested-by: jenkins

src/pld/certus.c

@@ -9,6 +9,7 @@
 #include "config.h"
 #endif
 
+#include "certus.h"
 #include "lattice.h"
 #include "lattice_cmd.h"
 

src/pld/ecp2_3.c

@@ -9,6 +9,7 @@
 #include "config.h"
 #endif
 
+#include "ecp2_3.h"
 #include "lattice.h"
 
 #define LSCC_REFRESH         0x23

src/pld/ecp5.c

@@ -9,6 +9,7 @@
 #include "config.h"
 #endif
 
+#include "ecp5.h"
 #include "lattice.h"
 #include "lattice_cmd.h"