arm64: guard asm/assembler.h against multiple inclusions
arm64: guard asm/assembler.h against multiple inclusions

asm/assembler.h lacks the usual guard against multiple inclusion,
leading to a compilation failure if it is accidentally included
twice.

Using the classic #ifndef/#define/#endif construct solves the issue.

Signed-off-by: Marc Zyngier <a16cc0c82647c52d401177f8e50567df5499e36c@arm.com>
Signed-off-by: Will Deacon <b913f13ef92ac157955c954ccaaff7be065faba4@arm.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs