arm64: update die handler from ARM / x86

Commit 02df19b4 ("ARM:
7424/1: update die handler from x86") refactored the ARM
die() logic to avoid a deadlock if a kernel oops happens
while holding a spinlock that may also be used in an IRQ
handler. Refactor the ARM64 die() handler in a similar way,
to avoid similar deadlocks, which would have otherwise
prevented the kernel from printing the full panic output
and properly completing the panic() path.

Change-Id: I217a8d719f64b54467fa88a583d83f72193d7580
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>