cmd: avb: Fix compiler warnings

When building U-Boot with AVB enabled, compiler shows next warnings:

    cmd/avb.c: In function 'do_avb_read_pvalue':
    cmd/avb.c:371:18: warning: format '%ld' expects argument of type
                      'long int', but argument 2 has type 'size_t'
                      {aka 'unsigned int'} [-Wformat=]
       printf("Read %ld bytes, value = %s\n", bytes_read,
                    ~~^                       ~~~~~~~~~~
                    %d

    cmd/avb.c: In function 'do_avb_write_pvalue':
    cmd/avb.c:404:19: warning: format '%ld' expects argument of type
                      'long int', but argument 2 has type '__kernel_size_t'
                      {aka 'unsigned int'} [-Wformat=]
       printf("Wrote %ld bytes\n", strlen(value) + 1);
                     ~~^           ~~~~~~~~~~~~~~~~~
                     %d

Fix those by using "%zu" specified.
Signed-off-by: NSam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: NIgor Opaniuk <igor.opaniuk@gmail.com>

cmd/avb.c

@@ -368,7 +368,7 @@ int do_avb_read_pvalue(cmd_tbl_t *cmdtp, int flag, int argc,
 
 	if (avb_ops->read_persistent_value(avb_ops, name, bytes, buffer,
 					   &bytes_read) == AVB_IO_RESULT_OK) {
-		printf("Read %ld bytes, value = %s\n", bytes_read,
+		printf("Read %zu bytes, value = %s\n", bytes_read,
 		       (char *)buffer);
 		free(buffer);
 		return CMD_RET_SUCCESS;
@@ -401,7 +401,7 @@ int do_avb_write_pvalue(cmd_tbl_t *cmdtp, int flag, int argc,
 	if (avb_ops->write_persistent_value(avb_ops, name, strlen(value) + 1,
 					    (const uint8_t *)value) ==
 	    AVB_IO_RESULT_OK) {
-		printf("Wrote %ld bytes\n", strlen(value) + 1);
+		printf("Wrote %zu bytes\n", strlen(value) + 1);
 		return CMD_RET_SUCCESS;
 	}