ANDROID: Sdcardfs: Move gid derivation under flag

This moves the code to adjust the gid/uid of lower filesystem
files under the mount flag derive_gid.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Change-Id: I44eaad4ef67c7fcfda3b6ea3502afab94442610c
Bug: 63245673
diff --git a/fs/sdcardfs/derived_perm.c b/fs/sdcardfs/derived_perm.c
index 1239d1c..fffaad4 100644
--- a/fs/sdcardfs/derived_perm.c
+++ b/fs/sdcardfs/derived_perm.c
@@ -176,6 +176,9 @@
 	gid_t gid = sbi->options.fs_low_gid;
 	struct iattr newattrs;
 
+	if (!sbi->options.gid_derivation)
+		return;
+
 	info = SDCARDFS_I(d_inode(dentry));
 	info_d = info->data;
 	perm = info_d->perm;