arm: mach-omap2: mux: fix buffer overrun

memcpy() copies 8 bytes too much (omap_mux_entry vs. omap_mux). Correct
by replacing memcpy() with struct assignment, which is safer.

Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>