mach-snapdragon: of_fixup: fix condition check in ft_board_setup()

mach-snapdragon: of_fixup: fix condition check in ft_board_setup()

The fdt_node_check_compatible() function returns 0 on success which is
pretty confusing, and we were using it wrong!

Invert the condition check and refactor things to be more readable.

Additionally, add the check for the RB1 which needs the same fixup as
the RB2.

Reported-by: Sam Day <me@samcday.com>
Fixes: e64503f1fcdf ("mach-snapdragon: implement ft_board_setup() for USB role selection")
Tested-by: Alexey Minnekhanov <alexeymin@postmarketos.org>
Tested-by: Sam Day <me@samcday.com>
Link: https://lore.kernel.org/r/20250331104327.321339-1-caleb.connolly@linaro.org
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>