Update CHANGELOG for 4.2.0 and collect Tested-by tags.

Signed-off-by: Joakim Bech <[email protected]>
Tested-by: Etienne Carriere <[email protected]> (stm32mp1-135F_DK w/ pkcs11)
Tested-by: Etienne Carriere <[email protected]> (stm32mp1-157C_DK2_SCMI w/ pkcs11)
Tested-by: Etienne Carriere <[email protected]> (stm32mp1-157C_EV1 w/ RPMB)
Tested-by: Imre Kis <[email protected]> (fvp-ts)
Tested-by: Jens Wiklander <[email protected]> (FVP)
Tested-by: Jens Wiklander <[email protected]> (Hikey)
Tested-by: Jens Wiklander <[email protected]> (imx-mx8mqevk)
Tested-by: Jerome Forissier <[email protected]> (rockchip-rk3399) (Rockpi4B)
Tested-by: Jerome Forissier <[email protected]> (vexpress-qemu_armv8a)
Tested-by: Jerome Forissier <[email protected]> (vexpress-qemu_virt)
Tested-by: Joakim Bech <[email protected]> (RPi 3B v1.2)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx6dlsabresd)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx6qsabresd)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx6sllevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx6ulevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx6ulzevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx7dsabresd)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx7ulpevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8dxlevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8mmevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8mnevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8mpevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8mqevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8qmmek)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8qxpmek)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx8ulpevk)
Tested-by: Sahil Malhotra <[email protected]> (imx-mx93evk)
Tested-by: Sahil Malhotra <[email protected]> (LS1012A-RDB)
Tested-by: Sahil Malhotra <[email protected]> (LS1046A-RDB)
Tested-by: Sahil Malhotra <[email protected]> (LX2160A-RDB)