Upgrade process always copied sdmc:/boot.firm to nand:/boot.firm even if
Luma3DS was chainloaded from another path.
Fix this by copying from argv[0], if Luma3DS was launched from the SD
card.
Also use "sdmc:" and "nand:" instead of "0:" and "1:" when using FatFS.
Closes#1776.
- Stop spamming mcu reads... use the GPIO pin to know if there's a MCU interrupt, instead
- Wait for the MCU interrupts to be raised when powering up LCD+backlights
- Also turn off LCD+backlight when needed