uClibc: fix sparc build breakage

Closes #4021

Fix build breakage for sparc as reported in bug #4021
Patches from Konrad Eisele <konrad@gaisler.com>
Submitted in the uclibc mailing list.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>