dmaengine: idma64: useless use of min_t()

We use a pattern

	x = min_t(u32, <LOG2_CONSTANT>, __ffs(expr));

There is no need to use min_t() since we can replace it by

	x = __ffs(expr | <2^LOG2_CONST>);

and moreover guarantee that argument of __ffs() will be not zero.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>