[MIPS] u-boot.lds: Cleanup __u_boot_cmd_{start,end}

Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
diff --git a/board/tb0229/u-boot.lds b/board/tb0229/u-boot.lds
index b2fa9f2..c629040 100644
--- a/board/tb0229/u-boot.lds
+++ b/board/tb0229/u-boot.lds
@@ -54,10 +54,11 @@
 
 	.sdata  : { *(.sdata) }
 
-	. = .;
-	__u_boot_cmd_start = .;
-	.u_boot_cmd : { *(.u_boot_cmd) }
-	__u_boot_cmd_end = .;
+	.u_boot_cmd : {
+	  __u_boot_cmd_start = .;
+	  *(.u_boot_cmd)
+	  __u_boot_cmd_end = .;
+	}
 
 	uboot_end_data = .;
 	num_got_entries = (__got_end - __got_start) >> 2;