of/platform: Allow secondary compatible match in of_dev_lookup

We currently try to match of_dev_auxdata based on compatible,
IO address, and device name. But in some cases we have multiple
instances of drivers that can use the same auxdata.

Let's add an additional secondary lookup for generic compatible
match for auxdata if no device specific match is found. This does
not change the existing matching, and still allows adding device
specific auxdata.

This simplifies things as specifying the IO address and device
name is prone errors as it requires maintaining an in kernel
database for each SoC.

To specify a generic match, all that is needed is to add a
OF_DEV_AUXDATA entry with no device instance specified:

OF_DEV_AUXDATA("pinctrl-single", 0, NULL, &pcs_pdata),

As the auxdata is already initialized only for the booted SoC,
there's not much of a chance of getting things wrong.

Let's also fix two checkpatch warnings while at it to add a
space before parenthesis in the for loop, and remove a comparison
to NULL by using !auxdata->compatible.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>