extcon: Fix some kernel-doc comments

extcon: Fix some kernel-doc comments

Add the description of @id in extcon_sync() kernel-doc comment
and @edev, @id, @prop in extcon_set_property_sync() kernel-doc
comment to remove warnings found by running scripts/kernel-doc,
which is caused by using 'make W=1'.
drivers/extcon/extcon.c:409: warning: Function parameter or
member 'id' not described in 'extcon_sync'
drivers/extcon/extcon.c:750: warning: Function parameter or
member 'edev' not described in 'extcon_set_property_sync'
drivers/extcon/extcon.c:750: warning: Function parameter or
member 'id' not described in 'extcon_set_property_sync'
drivers/extcon/extcon.c:750: warning: Function parameter or
member 'prop' not described in 'extcon_set_property_sync'

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>