[iOS] Fix to test for enterprise policy reason to disable sync

ProfileSyncService::GetDisableReasons() returns a flag, so a binary mask
should be used to test for the enterprise policy.

Bug introduced with:
crrev.com/c/1509412
crrev.com/c/1508262

Bug: 937118
Change-Id: I2b9a409d89ce67f249c3b4030658002cd5fd6516
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1529106
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641843}
2 files changed