platform/x86: silicom-platform: Add missing "Description:" for power_cycle sysfs attr

The Documentation/ABI/testing/sysfs-platform-silicom entry
for the power_cycle sysfs attr is missing the "Description:" keyword,
add this.

Signed-off-by: Hans de Goede <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/ABI/testing/sysfs-platform-silicom

···
 Date:		November 2023
 KernelVersion:	6.7
 Contact:	Henry Shi <[e-mail]>
+Description:
 		This file allow user to power cycle the platform.
 		Default value is 0; when set to 1, it powers down
 		the platform, waits 5 seconds, then powers on the