shader: fix conversion for return type of various bit operations
findLSB, findMSB, and countBits always return a signed integer
Fixes:
- dEQP-GLES31.functional.shaders.builtin_functions.uniform.findLSBMinusOne.*
- dEQP-GLES31.functional.shaders.builtin_functions.integer.findmsb.*
- dEQP-GLES31.functional.shaders.builtin_functions.integer.bitcount.*
Signed-off-by: Gert Wollny gert.wollny@collabora.com
Edited by Jakob Bornecrantz