Style fixes.
Be prepared that set_dumper() might fail even when resetting it or prefix
the call with (void) to document that we intentionally ignore the return
value - no way to handle an error in case of device disappearing.
Remove redundant call to ipsec_getpolicybyaddr().
ipsec_hdrsiz() will call it internally.

Sponsored by:	Yandex LLC
Make sure __ARM_ARCH is defined in sysreg.h by including acle-compat.h