usb: musb: omap2430: fix wrong devm_kzalloc() result check

Commit 00a0b1d5 (usb: musb: omap: Add device
tree support for omap musb glue) assigns result of devm_kzalloc() call to
the 'config' variable but then checks for NULL the 'data' variable (already
checked after previous call). Thus we risk a kernel oops further when data
pointed by 'config' is written to by subsequent of_property_read_u32() calls
iff the allocation happens to fail...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>