[Toybox] blkdiscard man page clarification

[Patrick Oppenlander]

Hi Lukas,

while writing a blkdiscard for toybox I came across a discrepancy
between the man page and the util-linux implementation.

For the offset and length arguments, the man page states that "The
provided value will be aligned to the device sector size", but the
implementation does not perform any alignment and returns an error.

% blkdiscard -o 99 /dev/sdc
blkdiscard: /dev/sdc: offset 99 is not aligned to sector size 512

To me, that behaviour makes sense.

A simple resolution would be to change the text to "The provided value
_must_ be aligned to the device sector size".

Kind regards,

Patrick