UPSTREAM: arm64: Ensure that the 'bti' macro is defined where linkage.h is included

Not all .S files include asm/assembler.h, however the SYM_FUNC_*
definitions invoke the 'bti' macro. Include asm/assembler.h in
asm/linkage.h.

Bug: 254441685
Fixes: 9be34be8 ("arm64: Add macro version of the BTI instruction")
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit dd73d18e)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ifa5f046d647a3ede82565436a70def87cf1b7ba2