OMAP2xxx clock: set up clockdomain pointer in struct clk

clock24xx.c is missing a omap2_init_clk_clkdm() in its
omap2_clk_init() function.  Among other bad effects, this causes the
OMAP hwmod layer to oops on boot.

Thanks to Carlos Aguiar <carlos.aguiar@indt.org.br> and Stefano
Panella <Stefano.Panella@csr.com> for reporting this bug.  Thanks to Tony
Lindgren <tony@atomide.com> for N800 booting advice.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Carlos Aguiar <carlos.aguiar@indt.org.br>
Cc: Stefano Panella <Stefano.Panella@csr.com>
Cc: Tony Lindgren <tony@atomide.com>