mach-snapdragon: do carveouts for qcs404 only

The newly introduced carve_out_reserved_memory causes issues when
U-Boot is chained from the lk2nd bootloader. lk2nd provides a
simple-framebuffer device and marks the framebuffer region as no-map in
the supplied /reserved-memory. Consequently, the simple_video driver
triggers a page fault when it tries to write to this region.

As per Caleb's advice, this simple patch only does the carveouts for the
qcs404 SoC for which it was originally designed. The intent is to do the
carveouts for more Qualcomm SoCs in future.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>