ARM: mm: fix numerous hideous errors in proc-arm740.S

The setup code in proc-arm740.S is completely broken and, as far as I
can tell, always has been. I was >this< close to ripping it out, when a
740t core-tile materialised in the office, so I've had a crack at fixing
things up:

	- Fix the ram/flash area calculations so that we actually set
	  the condition flags before testing them...
	- Fix the proc_info structure so that __cpu_io_mmu_flags are
	  defined as 0, placing the __cpu_flush pointer at the correct
	  offset
	- Re-number the registers used during __arm740_setup so that
	  we don't clobber the machine ID et al
	- Advertise Thumb support via the hwcaps, since 740T is the only
	  740 implementation.

Acked-by: Hyok S. Choi <hyok.choi@samsung.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>