selftests/nolibc: use EFI -bios for LoongArch qemu

qemu for LoongArch does not work properly with direct kernel boot.
The kernel will panic during initialization and hang without any output.

When booting in EFI mode everything work correctly.

While users most likely don't have the LoongArch EFI binary installed at
least an explicit error about 'file not found' is better than a hanging
test without output that can never succeed.

Link: https://lore.kernel.org/loongarch/1738d60a-df3a-4102-b1da-d16a29b6e06a@t-8ch.de/


Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20231031-nolibc-out-of-tree-v1-1-47c92f73590a@weissschuh.net