uio: Simplify uio error path by using devres functions

Using devres functions simplify driver error path.
- Use devm_kzalloc
- Use devm_request_irq

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>