ARM: msm: 8064: fix the SDC3 WP switch

Commit 48fc326d (msm: 8064: Disable write-protect for MTP/LIQUID)
while attempting to disable the wp gpio switch on MTP and LIQUID
accidentially set the wp gpio switch to zero.
Zero is a valid gpio number and therefore it was not really disabled.
Instead EINVAL should be used.

In addition commit c9fd7de5 (IFC6410: BSP: Initial support for Inforce
IFC6410 Single Board Computer (SBC)) added support for ifc6410 and used
the same code as commit 48fc326d for (not) disabling the wp gpio
switch on ifc6410. It was wrong in all terms, see the code:
--------------cut-------------------------
if (!machine_is_apq8064_cdp()) {
	apq8064_sdc3_pdata->wpswitch_gpio = 0;
	apq8064_sdc3_pdata->is_wpswitch_active_low = false;
}
if (!machine_is_apq8064_ifc6410()) {
	apq8064_sdc3_pdata->wpswitch_gpio = 0;
	apq8064_sdc3_pdata->is_wpswitch_active_low = false;
}
-------------cut--------------------------
The second if clause has no effect as the first if clause has ran
already, moreover, it has a negative effect of setting the wpswitch_gpio
to zero also on CDP board! That means that on all boards (including CDP) the
wpswitch_gpio is set to zero (which is a valid gpio) and not disabled.

Fix the above problem(s) by removing the second if clause and replacing 0
in the first if clause with -EINVAL. Also, remove the
is_wpswitch_active_low setting as once we have EINVAL in wpswitch_gpio,
the is_wpswitch_active_low is never parsed.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>