uclibc: rename SETUP_DOT_CONFIG to FIXUP_DOT_CONFIG

In a subsequent patch, the behavior of UCLIBC_SETUP_DOT_CONFIG will change
so that it only applies fixups to the (already copied) configuration file.
This patch renames this function to UCLIBC_FIXUP_DOT_CONFIG to better match
the future behavior.

Suggested-by: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>