[Bug target/60300] [avr] Suboptimal stack pointer manipulation for frame setup

[matthijs at stdin dot nl]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60300

--- Comment #1 from Matthijs Kooijman <matthijs at stdin dot nl> ---
I noticed I didn't use -O in the output I pasted, but I just confirmed that the
results are the same with -Os and -O3.