How to set Forced SD Boot Mode

With some specific abnormal operations, boot parts of SPI Flash can be corrupted.
In this case, OGA/OGS board can't enter a normal boot process even though a proper SD card is inserted,
because boot order priority of SPI Flash is higher than SD card's one.

Using a switch, SW18, you can make OGA/OGS to enter a forced SD boot mode regardless of SPI flash status.