thermal/x86_pkg_temp_thermal: Cosmetic: Rename internal variables to zones from packages

Syntax update only -- no logical or functional change.

In response to the new multi-die/package changes, update variable names to
use the more generic thermal "zone" terminology, instead of "package", as
the zones can refer to either packages or die.

Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Link: https://lkml.kernel.org/r/b65494a76be13481dc3a809c75debb2574c34eda.1557769318.git.len.brown@intel.com