ns16550: fix an incorrect assignment to uart->io_size

ns16550: fix an incorrect assignment to uart->io_size

uart->io_size represents the size in bytes. Thus, when serial_port.bit_width
is assigned to it, it should be converted to size in bytes.

Fixes: 17b516196c ("ns16550: add ACPI support for ARM only")
Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
master commit: 352c89f72ddb67b8d9d4e492203f8c77f85c8df1
master date: 2023-01-24 16:54:38 +0100