Revert "ANDROID: vfs: fix export symbol type"

This reverts commit 171b4c30 as sdcardfs
is no longer part of the kernel tree.

Bug: 157700134
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ia049e7149bf31d3fbc73bfdc1549dab780288963