wlfreerdp: fix compilation errors

This commit fixes the following errors by removing or replacing old functions:
wlfreerdp.c:(.text.startup+0xc): undefined reference to freerdp_channels_global_init
wlfreerdp.c:(.text.startup+0x72): undefined reference to freerdp_client_parse_command_line_arguments
wlfreerdp.c:(.text.startup+0x9b): undefined reference to freerdp_channels_global_uninit