board: xilinx: Add missing prototypes

Add missing prototypes to fix the below sparse warnings
1. warning: no previous prototype for 'soc_name_decode'
[-Wmissing-prototypes]
2. warning: no previous prototype for 'soc_detection'
[-Wmissing-prototypes]
3. warning: no previous prototype for 'board_name_decode'
[-Wmissing-prototypes]
4. warning: no previous prototype for 'board_detection'
[-Wmissing-prototypes]

Signed-off-by: Algapally Santosh Sagar <santoshsagar.algapally@amd.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@amd.com>
Link: https://lore.kernel.org/r/20230523055626.14742-1-ashok.reddy.soma@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/board/xilinx/common/board.h b/board/xilinx/common/board.h
index 69e6424..922c9d5 100644
--- a/board/xilinx/common/board.h
+++ b/board/xilinx/common/board.h
@@ -11,4 +11,11 @@
 
 int xilinx_read_eeprom(void);
 
+char *board_name_decode(void);
+
+bool board_detection(void);
+
+char *soc_name_decode(void);
+
+bool soc_detection(void);
 #endif /* BOARD_XILINX_COMMON_BOARD_H */