Tag all references to assembly functions with SYM_TYPED_FUNC_START()
and SYM_FUNC_END() so they also become CFI-safe.

When we add SYM_TYPED_FUNC_START() to assembly calls, a function
prototype signature will be emitted into the object file at
(pc-4) at the call site, so that the KCFI runtime check can compare
this to the expected call. Example:

8011ae38:       a540670c        .word   0xa540670c

8011ae3c <v7_flush_icache_all>:
8011ae3c:       e3a00000        mov     r0, #0
8011ae40:       ee070f11        mcr     15, 0, r0, cr7, cr1, {0}
8011ae44:       e12fff1e        bx      lr

This means no "fallthrough" code can enter a SYM_TYPED_FUNC_START()
call from above it: there will be a function prototype signature
there, so those are consistently converted to a branch or ret lr
depending on context.
Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>