mmc: sdio_uart: fix xmit_fifo leak when the port table is full

In the Linux kernel, the following vulnerability has been resolved: mmc: sdio_uart: fix xmit_fifo leak when the port table is full sdio_uart_add_port() allocates the transmit fifo before claiming a slot in sdio_uart_table[]. When all UART_NR slots are taken, it returns -EBUSY with the fifo still allocated, but the probe error path only kfree()s the port, leaking the transmit fifo. Free the fifo in the failure path of sdio_uart_add_port() itself so the function retains nothing on error.