mediatek: mt7622: clean up image build

mediatek: mt7622: clean up image build

 * clean up whitespace to make GPT partitioning more readable
 * don't select packages already part of the target default selection
 * don't select U-Boot variants (breaks ImageBuilder)
 * don't select AHCI on boards without SATA
 * don't select kmod-usb2 and kmod-ohci, USB 1.x and USB 2.0 devices
   work fine with the in-SoC XHCI host having just kmod-usb3 installed.
 * select kmod-btmtkuart for devices with Bluetooth support
 * sort DEVICE_PACKAGES

Signed-off-by: Daniel Golle <daniel@makrotopia.org>