libpayload needs a static copy of the out of line function
`font_glyph_filled()` in every TU that needs it. So make it static
inline.
This fixes a build error by gcc (Debian 7.1.0-12) 7.1.0 from Debian
Sid/unstable. This happens with any libpayload based payload like
coreinfo, nvramcui or tint.
```
[…]
LPCC build/coreinfo.elf (LINK)
/src/coreboot/payloads/coreinfo/build/libpayload/bin/../lib/libpayload.a(corebootfb.libc.o): In function `corebootfb_putchar':
/src/coreboot/payloads/libpayload/drivers/video/corebootfb.c:173: undefined reference to `font_glyph_filled'
[…]
```
Change-Id: I931f0f17b33abafdc49aa755a0dad65e28820750
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/20897
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>