ish: refactor statistic collection and command
ish: refactor statistic collection and command

This commit re-writes the power manangment statistic collection and
idlestats command to no longer use conditional compilation, and to
reduce repetitive code.

BUG=b:132178013,b:132929262
BRANCH=none
TEST=observed output of idlestats command on arcada_ish, everything
appears to be normal

Change-Id: I3075eba2ae3f681a2d7d1891f5014de4b6db24a2
Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1617079
Legacy-Commit-Queue: Commit Bot <5c2bf027dc5cc7ef186314391646e49f6866dc00@chromium.org>
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec