USB: serial: f81534: fix reading old/new IC config

USB: serial: f81534: fix reading old/new IC config

The F81532/534 had a internal configuration space to save & control
IC state with address F81534_CUSTOM_ADDRESS_START (0x2f00). Layout
as following:
	+00h: to indicate the section is valid
	+01h~04h: UART Mode & port availability
	+05h~08h: Output pin control on IC power on
	+09h~12h: Output pin control on working <-- New added

Old driver will use +05~08h as default on working, but newer IC will
configed with shutdown mode(7) in 05h~08h and working mode with RS232(1)
in 09h~12h. It'll make mainstream driver not working.

This patch will make mainstream driver compatible older and newer IC.
If using a old IC, the +05h~08h will be 00h~06h, we'll direct apply it.
If using a new IC, the +05h~08h will be 07h or larger, we'll read +09h~12h
to apply newer configuration.

Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>