staging: ft1000-usb: check for errors in card_send_command

kmalloc() result check was lacking. Fixing that required also
changing card_send_command() return type from void to int, and
checking its return code everywhere.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=78561


Reported-by: Maksymilian Arciemowicz <max@cert.cx>
Signed-off-by: Andrey Utkin <andrey.krieger.utkin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>