Camera2: Fix FPS value scaling between HAL2 and API

API assumes FPS values are in fixed-point with LSB 0.001; HAL2 just
uses ints with no fractional part.

HAL should probably use floats or something similar, but for now, fix
scaling so the two agree on FPS values.

Bug: 7230239
Change-Id: Ie18a4f11fc9d17d9ae2d04781511a273213eda55