Add missing @ tags for some rpmsg_eptdev structure parameters.
This fixes warning messages on build:
drivers/rpmsg/rpmsg_char.c:75: warning: Function parameter or struct member 'remote_flow_restricted' not described in 'rpmsg_eptdev'
drivers/rpmsg/rpmsg_char.c:75: warning: Function parameter or struct member 'remote_flow_updated' not described in 'rpmsg_eptdev'
Fixes: 5550201c0fe2 ("rpmsg: char: Add RPMSG GET/SET FLOWCONTROL IOCTL support")
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>