smc91111: Move driver attach prototype to header file.

Also signal to compiler that the start variable in lan91cxx_recv is only used when debugging.
bsps/sparc: Make local functions static.

The PCI and RASTA versions of the uart, spacewire and 1553 drivers directly includes the c-file of the standard versions
of the drivers, but uses a macro to change the name of the driver register function. When the standard version is
used this function should be global, when it is included as part of the PCI and RASTA versions it should be local and
static.
bsps/sparc: Make spurious trap handler function static.
bsps/sparc: Change asm to __asm__ to compile with -pedantic.
greth: Make local functions static, remove overflow and correct printf call.