Dump gralloc information in dumpsys gfxinfo

This is really handy information to have and
even though it's not strictly speaking in the realm
of what gfxinfo is responsible for, it's a good-enough
place to shove it so why not

Test: dumpsys gfxinfo com.android.systemui
Change-Id: I11982eca9460a38471bbb4eab019b2335f6b13a4