MIPS: fix __raw_* IO accessors

The purpose of the __raw* IO accessors is to provide
IO access in native-endian order. However in the current
MIPS implementation, the 16 and 32 bit variants of the
__raw accessors are swapping the values on big-endian
systems if the CONFIG_SWAP_IO_SPACE option is enabled.

The patch changes the IO accessor macros to fix this
broken behaviour.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>
MIPS: asm/errno.h: switch to asm-generic/errno.h

This fixes several warnings like

In file included from ./u-boot/include/linux/mtd/mtd.h:13:0,
                 from env_onenand.c:37:
./u-boot/build/vct_platinumavc_onenand_small/include2/asm/errno.h:52:0: warning: "ENOMSG" redefined [enabled by default]

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>