KernelWakelockReader: reuse buffer when parsing

Eliminates 32 kb buffer allocation every time readKernelWakelockStats()
is called.

Test: atest FrameworksCoreTests:KernelWakelockReaderTest
Test: "dumpsys batterystats --checkin" contains kernel wake lock
information.
Change-Id: Ifc7254ab3a5272b056cbc75233aa2dfa8219ea84
1 file changed