include: <asm-generic/atomic.h>: remove stub IRQ save/restore ...

For an architecture to use <asm-generic/atomic.h>, it must define
local_irq_save() and local_irq_restore(). Instead of having every
platform define duplicate their stub definition, just drop them
altogether, so <asm-generic/atomic.h> can be used freestanding.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ARM: atomic.h: move generic implementation to asm-generic ...

For easier code-sharing, the UBIFS code still uses the Linux atomic
accessors.  Make porting it to sandbox easier, by providing these
functions for all platforms.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>