Enable dynamic read logs buffer sizing for incfs

Default buffer size of 4 pages causes many missed log records
because of ring buffer overflows. This change adds a dynamic
sizing, up to 32 pages, that has shown to decrease dropped
records pretty much to nil

Fallback code automatically decreases the buffer size in case
of kernel memory fragmentation - some logs are still much
better than no logs at all

Bug: 203551890
Test: manual, adb install <Apk>; checked for fallback by
  increasing max size to 1024 pages
Change-Id: I0ea46c1ad2534b1dbb5faaead52afab88b66747b