Remove "explicit" from HardwareBuffer move constructor

Clang-tidy gives the following lint message:
"Move constructor should not be declared explicit"

This CL applies the fix and removes "explicit".

Bug: N/A
Test: mma
Change-Id: I5135aca1a1cf37d92f4561d90d34c00247804d7e
Merged-In: I5135aca1a1cf37d92f4561d90d34c00247804d7e
(cherry picked from commit 8d29e6f0)