.gitattributes: Remove special text handling of stm32 usbdev files.
tests/basics/string_cr_conversion.py -text
tests/basics/string_crlf_conversion.py -text
ports/stm32/pybcdc.inf_template -text
-ports/stm32/usbd_* -text
-ports/stm32/usbdev/** -text
ports/stm32/usbhost/** -text
ports/cc3200/hal/aes.c -text
ports/cc3200/hal/aes.h -text
