Avoid read barrier for image HLoadClass

Concurrent copying baker:

X86_64 core-optimizing-pic.oat: 28583112 -> 27906824 (2.4% smaller)

Around 0.4% of 2.4% is from re-enabling kBootImageLinkTimeAddress,
kBootImageLinkTimePcRelative, and kBootImageAddress.

N6P boot.oat 32: 73042140 -> 71891956 (1.57% smaller)
N6P boot.oat 64: 83831608 -> 82531456 (1.55% smaller)

EAAC: 1252 -> 1245 (32 samples)

Bug: 29516974

Test: test-art-host CC baker, N6P booting

Change-Id: I9a196cf0157058836981c43c93872e9f0c4919aa