Non-root access to /proc/allocinfo

Change group and permissions to the /proc/allocinfo file, so that the
file is readable from non-root.

Bug: 384777823
Test: adb shell dumpstate
Change-Id: Icf5331cb68e4b706d4eaf11ee2576234c2d7789f
Signed-off-by: Alessio Balsini <balsini@google.com>