[ARM] pxa: remove left-over struct clk *other field from struct clk

Its removal was omitted when all its uses were removed in 8c3abc7d...
"[ARM] pxa: convert to clkdev and match clocks by struct device where possible"

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>