phy: fix kernel oops in phy_lookup()

phy: fix kernel oops in phy_lookup()

The kernel oopses in phy_lookup() due to 'phy->init_data' being NULL if we
register PHYs from a device tree probing driver and then call phy_get() on a
device that has no representation in the device tree (e.g. a PCI device).
Checking the pointer before dereferening it and skipping an interation if
it's NULL prevents this kernel oops.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[backport from upstream commit 743bb387a1edbf1ebbba6cf77c1af3e488886c39]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-Id: Iea16343af63965d19960fc8acf89e0a65b806440