Subzero: Fix a debugging string in the test_icmp crosstest.
Subzero: Fix a debugging string in the test_icmp crosstest.

STR(inst) should be STR(cmp).

BUG=none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/466543002

bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,google/swiftshader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader