DO NOT MERGE: Fix signature of KernelCpuProcReader

Signatures of blacklist APIs were frozen with Pi release. Need to update
the signature manually for a change to KernelCpuProcReader introduced in
ag/5055721.

Bug: 111805985
Fixes: 117089824
Test: Manual build
Test: HiddenApiTest#testSignature
Change-Id: I2918afa813417e05f3f0578575a7051fd147aa1a