UPSTREAM: Documentation: Fix index.rst after psci.rst renaming

Fix the TOC in index.rst after psci.rst has been renamed to
hypercalls.rst.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20220504205627.18f46380@canb.auug.org.au


(cherry picked from commit c36820b0)
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 233587962
Bug: 233588291
Change-Id: I40e6ebffb2ec6c04464dfe42eb99fb7e286413d6