All other uses of "asm goto" go through asm_volatile_goto, which avoids
a miscompile when using GCC < 4.8.2. Replace our open-coded "asm goto"
statements with the asm_volatile_goto macro to avoid issues with older
toolchains.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: NMiguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>