utils: Update the way to find apu core

during upstreaming process of the kernel driver, one of the maintainer's request was to use rproc = devm_rproc_alloc(dev, dev_name(dev), ... ) instead of proc = rproc_alloc(dev, "apu", ...)

changing the name of the remoteproc device from apu to XXXXXXXX.apu where XXXXXXXX is the register adress of the apu

To fix this, implement a new helper function to locate a substring instead of a string

In order to be backward compatible, also check for vpu substring instead of apu

Signed-off-by: Alexandre Bailon abailon@baylibre.com Signed-off-by: Julien Stephan jstephan@baylibre.com