MLK-11657: IPU: check ldb clock with clk name

MLK-11657: IPU: check ldb clock with clk name

4.1 kernel apply the followed patch:
commit 73e0e496afdac9a5190eb3b9c51fdfebcc14ebd4
clkdev: Always allocate a struct clk and call __clk_get() w/ CCF

clock_get will return a new struct clk, so we can't use the pointer
of clk struct to compare clk whether is equal, replace with clk name.

Signed-off-by: Sandor Yu <R01008@freescale.com>