Documentation/features/vm: riscv supports THP now

After commit e88b3331 ("riscv: mm: add THP support on 64-bit"),
riscv can support THP.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20210805002739.23f44d2d@xhacker


Signed-off-by: Jonathan Corbet <corbet@lwn.net>