drivers: usb_dc_stm32: Make pin remapping part of the device tree

The SYSCFG_CFGR1_PA11_PA12_RMP define is present even on packages where
the remap isn't strictly required. This commit makes the remap optional
based on a DT property.

Also fixes syntax error caused by a missing );.

Signed-off-by: Josef Gajdusek <atx@atx.name>