earlycon: provide early_avail() routine

Signed-off-by: Andrew 'Necromant' Andrianov <andrew@ncrmnt.org>
lib: Implement earlycon for 8051/STC

Signed-off-by: Andrew 'Necromant' Andrianov <andrew@ncrmnt.org>
8051: Use --stack-auto by default

This avoids poisoning libs with __reentrant

Signed-off-by: Andrew 'Necromant' Andrianov <andrew@ncrmnt.org>
buildsystem: Update .gitignore

Signed-off-by: Andrew 'Necromant' Andrianov <andrew@ncrmnt.org>