Add 40fps as a FPS option

40fps is a valid frame rate for a 120Hz display
since 40 is a divisor of 120. Though it is not a common FPS
for games, in compliance with CTS test we need to add it.

Bug: b/204322816, b/206128693
Test: atest GameManagerServiceTests
      atest FrameRateOverrideHostTest
Change-Id: I2a2cf9d88c269dee388c8fe68e82df3514f4a9f1