options: Add support hex value to ignore_error

options: Add support hex value to ignore_error

The 'ignore_error=str' option expects either the name or the numeric
value of the errno in string format.  With recent additions like
io_uring_cmd ioengine, it's been possible to check not only errno values
but also the actual status values provided by the storage device.

Given that most status codes in NVMe specs are represented in
hexadecimal, specifying error values in hexadecimal is also useful to
ignore some errors.

For example, DULBE (Deallocated or Unwritten Logical Block Error) status
code can be ignored:

	ignore_error=0x287

Signed-off-by: Minwoo Im <minwoo.im@samsung.com>