clk: bcm281xx: don't use unnamed structs or unions

The Broadcom Kona clock code, as originally written, made use of
unnamed union and struct fields.  This is a feature present in C11,
and is a GNU extension otherwise.  It worked very well for me.

Unfortunately, Russell King reported that this feature was not
supported in a build environment he used, which meant attempting
to build this code failed spectacularly.

Add names to these unnamed fields, and update the code accordingly.

Reported-by: Russell King <linux@arm.linux.org.uk>
Tested-by: Markus Mayer <markus.mayer@linaro.org>
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>