lib/pattern: Support short repeated read calls when loading from file

lib/pattern: Support short repeated read calls when loading from file

Once a pattern file can be much larger, it will be possible that
kernel will return a short read while loading the file and thus may
randomly only load part of the file.

Fix this by putting the read in a loop so the entire file will be
read.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>