u-boot: vf610_qspi: Add qspi_erase_cmd to qspi driver

This command allow the user to erase a sector of size = 0x10000
bytes of the qspi memory from the address passed as argument.
The usage is as follows:

    qspierase addr
	Example:
	    qspierase 0x20040000

Signed-off-by: Juan Gutierrez <b44802@freescale.com>

drivers/spi/vf610_qspi.c

@@ -477,3 +477,23 @@ U_BOOT_CMD(
 	"		qspiinit dev=0 fa1=0x21000000 fb1=0x22000000\n"
 	""
 );
+
+int quadspi_erase_cmd(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	ulong addr;
+
+	if (argc < 2)
+		return CMD_RET_USAGE;
+
+	addr = simple_strtoul(argv[1], NULL, 16);
+	quadspi_erase_sector(addr);
+	return 0;
+}
+U_BOOT_CMD(
+        qspierase, 2, 0, quadspi_erase_cmd,
+	"Erase whole QSPI memory",
+        "qspierase addr\n"
+        "	Example:\n"
+	"	    qspierase 0x20040000\n"
+	""
+);