UPSTREAM: arm64: doc: Add brk/mmap/mremap() to the Tagged Address ABI Exceptions

Prior to commit dcde237319e6 ("mm: Avoid creating virtual address
aliases in brk()/mmap()/mremap()"), the kernel allowed tagged addresses
to be passed to the brk/mmap/mremap() syscalls. This relaxation was
tightened in 5.6 (backported to stable 5.4) but the
tagged-address-abi.rst document was only partially updated.

Bug: 254441685
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: dcde237319e6 ("mm: Avoid creating virtual address aliases in brk()/mmap()/mremap()")
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20210423175134.14838-1-catalin.marinas@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 75516c75a72b5629736c611cf45058d95978a9f2)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I3cb5b63764bd094cfa0f0d3db5b2505be03daa3a