staging: wilc1000: use flexible-array member instead of zero-length array

Use flexible-array member introduced in C99 instead of zero-length
array. Most of zero-length array was already taken care in previous
patch [1]. Now modified few more cases which were not handled earlier.

[1]. https://patchwork.kernel.org/patch/11394197/Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Link: https://lore.kernel.org/r/20200302162226.4196-4-ajay.kathat@microchip.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wilc1000/spi.c

@@ -109,27 +109,27 @@ struct wilc_spi_cmd {
 	union {
 		struct {
 			u8 addr[3];
-			u8 crc[0];
+			u8 crc[];
 		} __packed simple_cmd;
 		struct {
 			u8 addr[3];
 			u8 size[2];
-			u8 crc[0];
+			u8 crc[];
 		} __packed dma_cmd;
 		struct {
 			u8 addr[3];
 			u8 size[3];
-			u8 crc[0];
+			u8 crc[];
 		} __packed dma_cmd_ext;
 		struct {
 			u8 addr[2];
 			__be32 data;
-			u8 crc[0];
+			u8 crc[];
 		} __packed internal_w_cmd;
 		struct {
 			u8 addr[3];
 			__be32 data;
-			u8 crc[0];
+			u8 crc[];
 		} __packed w_cmd;
 	} u;
 } __packed;