regulator: ab8500-ext: Remove unnecessary checking for ab9540 and ab8540

This code was added by commit 0fe17e20
"regulator: ab8500-ext: Add support for AB9540 regulators"
and commit bd44e2cb "regulator: ab8500: Also check for AB8505 based platforms"

The original patch[1] is to set info->desc.ops = &ab9540_ext_regulator_ops.

However, ab9540_ext_regulator_ops is identical to ab8500_ext_regulator_ops[2].
Thus we can complete remove the unnecessary checking for ab9540 and ab8540.

[1] https://lkml.org/lkml/2013/3/28/333
[2] https://lkml.org/lkml/2013/4/1/178



Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>