asm-generic: Consolidate errno.h to asm-generic/errno.h

This patch use blackfin errno.h implementation which
correspond Linux kernel one.

MIPS implemetation is different that's why I keep it.

I removed ppc_error_no.h from Marvell boards which
was the same too.

I have got ack from ppc40x, blackfin, arm, coldfire and avr custodians.

Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Michal Simek <monstr@monstr.eu>