ARM: OMAP: use consistent error checking

Consistently check errors using the usual method used in the kernel
for much of its history.  For instance:

int gpmc_cs_set_timings(int cs, const struct gpmc_timings *t)
{
	int div;
	div = gpmc_calc_divider(t->sync_clk);
	if (div < 0)
		return div;
static int gpmc_set_async_mode(int cs, struct gpmc_timings *t)
{
...
	return gpmc_cs_set_timings(cs, t);

.....
	ret = gpmc_set_async_mode(gpmc_onenand_data->cs, &t);
	if (IS_ERR_VALUE(ret))
		return ret;

So, gpmc_cs_set_timings() thinks any negative return value is an error,
but where we check that in higher levels, only a limited range are
errors...

There is only _one_ use of IS_ERR_VALUE() in arch/arm which is really
appropriate, and that is in arch/arm/include/asm/syscall.h:

static inline long syscall_get_error(struct task_struct *task,
				     struct pt_regs *regs)
{
	unsigned long error = regs->ARM_r0;
	return IS_ERR_VALUE(error) ? error : 0;
}

because this function really does have to differentiate between error
return values and addresses which look like negative numbers (eg, from
mmap()).

So, here's a patch to remove them from OMAP, except for the above.

Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>