clk: Get rid of HAVE_MACH_CLKDEV

This config was used for the ARM port so that it could use a
machine specific clkdev.h include, but those are all gone now.
The MIPS architecture is the last user, and from what I can tell
it doesn't actually use it anyway, so let's remove the config all
together.

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Joshua Henderson <joshua.henderson@microchip.com>