regulator: core: fix the broken behavior of regulator_dev_lookup()

The behavior of regulator_dev_lookup() for non-DT way has been broken
since the commit b8c325545714 ("regulator: Move OF-specific regulator
lookup code to of_regulator.c").

Before the commit, of_get_regulator() was used to get the regulator,
which returns NULL if the regulator is not found. So the regulator
will be looked up through regulator_lookup_by_name() if no matching
regulator is found in regulator_map_list.

However, currently, of_regulator_dev_lookup() is used to instead of
of_get_regulator(), but the variable 'r' is set to ERR_PTR(-ENODEV)
instead of NULL if the regulator is not found. In this case, if no
regulator is found in regulator_map_list, the variable 'r' is still
ERR_PTR(-ENODEV), So regulator_dev_lookup() returns the value of 'r'
directly instead of continuing to look up the regulator through
regulator_lookup_by_name().

Fixes: b8c325545714 ("regulator: Move OF-specific regulator lookup code to of_regulator.c")
Signed-off-by: Wei Fang <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/core.c

···
 			return r;
 		if (PTR_ERR(r) == -EPROBE_DEFER)
 			return r;
+
+		if (PTR_ERR(r) == -ENODEV)
+			r = NULL;
 	}
 
 	/* if not found, try doing it non-dt way */