Microsoft has published technical specification for exFAT [1]
and the driver has been added to Linux staging tree [2].

It's now safe to drop BUILD_PATENTED label.

[1] https://docs.microsoft.com/windows/win32/fileio/exfat-specification
[2] http://lkml.iu.edu/hypermail/linux/kernel/1908.3/04254.html

Signed-off-by: DENG Qingfang <dengqf6@mail2.sysu.edu.cn>