quota: split out compat_sys_quotactl support from quota.c

Instead of adding ifdefs just split it into a new file.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/quota/Kconfig b/fs/quota/Kconfig
index efc02eb..dad7fb2 100644
--- a/fs/quota/Kconfig
+++ b/fs/quota/Kconfig
@@ -59,3 +59,8 @@
 	bool
 	depends on XFS_QUOTA || QUOTA
 	default y
+
+config QUOTACTL_COMPAT
+	bool
+	depends on QUOTACTL && COMPAT_FOR_U64_ALIGNMENT
+	default y