staging: iio: adc: use DIV_ROUND_UP

The kernel.h macro DIV_ROUND_UP performs the computation (((n) + (d) - 1) /
(d)) but is perhaps more readable.

Coccinelle script used :

// <smpl>
@haskernel@
@@
@depends on haskernel@
expression n,d;
@@
(
- (n + d - 1) / d
+ DIV_ROUND_UP(n,d)
|
- (n + (d - 1)) / d
+ DIV_ROUND_UP(n,d)
)
@depends on haskernel@
expression n,d;
@@
- DIV_ROUND_UP((n),d)
+ DIV_ROUND_UP(n,d)
@depends on haskernel@
expression n,d;
@@
- DIV_ROUND_UP(n,(d))
+ DIV_ROUND_UP(n,d)
// </smpl>

Signed-off-by: Tapasweni Pathak <tapaswenipathak@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>