mkbootimg: use stamp file for rpiboot, uppercase FAT label
fstab: USB drives don't support TRIM — requesting discard stalls jbd2
journal commits and causes Watchdog kills. Add fstab.rpi5.discard for
devices that do support TRIM (SD card, SSD); select via
BOARD_STORAGE_SUPPORTS_DISCARD := true in BoardConfig.mk.
mkbootimg: stamp file fixes ninja 'outputs should be files' warning.
Uppercase BOOT label suppresses mkfs.fat lowercase label warning.
oxmc
6afef06aa1