atapi_drv: Implement LBA48 specific block count

Use NATIVE MAX ADDRESS EXT to retrieve last block for LBA48. Also check not only
for enabled LBA48 support but for the 'host protected area' bit before using the
LBA48 version. This is because the high order byte (HOB) data retrieval is
broken in Qemu.

Fixes #761.
Add -mcpu flag to ARM CPU spec files (Ref #797)

When using certain assembler instructions, e.g. 'smc' that are
only available on some CPUs of the same architecture like ARMv7a,
it's necessary to specify the target CPU for the assembler. Otherwise
it will complain about.
run: disable network tests for imx53

We have no network driver on this platform by now.
Disable noux run script for i.MX53 platform

This platform misses necessary UART driver support.
run: add success message to lx_hybrid_pthread_ipc