Round up virtual display refresh rate

This semantics guarantees the virtual display will at least have the
specified refresh rate, e.g., if 60hz is requested on a 90hz display,
the virtual dislay will get a 90hz.

Bug: 266965278
Test: atest libsurfaceflinger_unittest
Change-Id: Ie7b30c5766454d0ad25cfd437f0498594c690a2e