reset: fix of_reset_control_get_count kerneldoc comment

Add a newline and remove a superfluous kerneldoc marker before the
of_reset_control_get_count kerneldoc comment, to fix documentation
build warnings:

  ./drivers/reset/core.c:832: warning: Incorrect use of kernel-doc format:  * of_reset_control_get_count - Count number of resets available with a device
  ./drivers/reset/core.c:840: warning: Function parameter or member 'node' not described in 'of_reset_control_get_count'

Fixes: 17c82e20

 ("reset: Add APIs to manage array of resets")
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>