arm64: add __nocfi to functions that jump to a physical address

Disable CFI checking for functions that switch to linear mapping and
make an indirect call to a physical address, since the compiler only
understands virtual addresses and the CFI check for such indirect calls
would always fail.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-15-samitolvanen@google.com