Simplify kconfig wording of thread support
Simplify kconfig wording of thread support

Use a choice for thread support selection.

Signed-off-by: Bernhard Reutner-Fischer <ce1ac9e9ad16abccd7821f371ad381197b4768ac@gmail.com>

m-labs/uclibc-lm32,skristiansson/uClibc-or1k,atgreen/uClibc-moxie,majek/uclibc-vx32,kraj/uClibc,skristiansson/uClibc-or1k,foss-xtensa/uClibc,czankel/xtensa-uclibc,groundwater/uClibc,kraj/uClibc,hjl-tools/uClibc,ddcc/klee-uclibc-0.9.33.2,foss-for-synopsys-dwc-arc-processors/uClibc,ysat0/uClibc,OpenInkpot-archive/iplinux-uclibc,groundwater/uClibc,mephi42/uClibc,czankel/xtensa-uclibc,hjl-tools/uClibc,kraj/uclibc-ng,majek/uclibc-vx32,wbx-github/uclibc-ng,skristiansson/uClibc-or1k,wbx-github/uclibc-ng,majek/uclibc-vx32,groundwater/uClibc,brgl/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,waweber/uclibc-clang,wbx-github/uclibc-ng,foss-xtensa/uClibc,brgl/uclibc-ng,ddcc/klee-uclibc-0.9.33.2,atgreen/uClibc-moxie,atgreen/uClibc-moxie,kraj/uClibc,ffainelli/uClibc,waweber/uclibc-clang,kraj/uclibc-ng,m-labs/uclibc-lm32,foss-for-synopsys-dwc-arc-processors/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,hwoarang/uClibc,ysat0/uClibc,ndmsystems/uClibc,ndmsystems/uClibc,groundwater/uClibc,groundwater/uClibc,hjl-tools/uClibc,atgreen/uClibc-moxie,brgl/uclibc-ng,ysat0/uClibc,waweber/uclibc-clang,majek/uclibc-vx32,m-labs/uclibc-lm32,ndmsystems/uClibc,wbx-github/uclibc-ng,ffainelli/uClibc,skristiansson/uClibc-or1k,ysat0/uClibc,ffainelli/uClibc,mephi42/uClibc,OpenInkpot-archive/iplinux-uclibc,m-labs/uclibc-lm32,ffainelli/uClibc,OpenInkpot-archive/iplinux-uclibc,hjl-tools/uClibc,OpenInkpot-archive/iplinux-uclibc,kraj/uClibc,kraj/uclibc-ng,ddcc/klee-uclibc-0.9.33.2,ndmsystems/uClibc,ddcc/klee-uclibc-0.9.33.2,ffainelli/uClibc,foss-xtensa/uClibc,czankel/xtensa-uclibc,czankel/xtensa-uclibc,mephi42/uClibc,brgl/uclibc-ng,waweber/uclibc-clang,mephi42/uClibc,foss-xtensa/uClibc,kraj/uclibc-ng,hwoarang/uClibc,hwoarang/uClibc,hwoarang/uClibc,hjl-tools/uClibc