[PATCH net-next v2 05/10] drivers: base: Add device_find_class()

Add a helper function to lookup a device reference given a class name.
This is a preliminary patch to remove adhoc code from net/dsa/dsa.c and
make it more generic.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 drivers/base/core.c    | 19 +++++++++++++++++++
 include/linux/device.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 020ea7f05520..3dd6047c10d8 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c

@@ -2065,6 +2065,25 @@ struct device *device_find_child(struct device *parent, void *data,
 }
 EXPORT_SYMBOL_GPL(device_find_child);
 
+static int dev_is_class(struct device *dev, void *class)