arm64: asm-bug: Renumber macro local labels to avoid clashes

Currently ASM_BUG() and its constituent macros define local
assembler labels 0, 1 and 2 internally, which carries a high risk
of clash with callers' labels and consequent mis-assembly.

This patch gives the labels a big random offset to minimise the
chance of such errors.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>