fastboot: Use const qualifier for char *part_name

In fastboot_*_get_part_info() functions we can use stronger typing by
expecting const strings.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Igor Opaniuk <igor.opaniuk@toradex.com>
diff --git a/include/fb_mmc.h b/include/fb_mmc.h
index fd5db9e..95db001 100644
--- a/include/fb_mmc.h
+++ b/include/fb_mmc.h
@@ -14,7 +14,8 @@
  * @part_info: Pointer to returned disk_partition_t
  * @response: Pointer to fastboot response buffer
  */
-int fastboot_mmc_get_part_info(char *part_name, struct blk_desc **dev_desc,
+int fastboot_mmc_get_part_info(const char *part_name,
+			       struct blk_desc **dev_desc,
 			       disk_partition_t *part_info, char *response);
 
 /**
diff --git a/include/fb_nand.h b/include/fb_nand.h
index 08ab0e2..6d7999f 100644
--- a/include/fb_nand.h
+++ b/include/fb_nand.h
@@ -16,8 +16,8 @@
  * @part_info: Pointer to returned part_info pointer
  * @response: Pointer to fastboot response buffer
  */
-int fastboot_nand_get_part_info(char *part_name, struct part_info **part_info,
-				char *response);
+int fastboot_nand_get_part_info(const char *part_name,
+				struct part_info **part_info, char *response);
 
 /**
  * fastboot_nand_flash_write() - Write image to NAND for fastboot