[regression] Screen turns off after exiting UEFI boot services

[X547]

Regression introduced in VisionFive2 Software v3.4.5, worked fine in v3.1.5.

Firmware should keep display engine enabled after exiting UEFI boot services according UEFI spec. Issue makes impossible to use display for operating systems that do not implements its own display engine driver.

Display 1920x1080 connected to HDMI port is used.

[X547]

Regression seems caused by 26a31fa.

CC: @kJugg