mesa: Use bitmask/ffs to iterate SamplersUsed
mesa: Use bitmask/ffs to iterate SamplersUsed

Replaces an iterate and test bit in a bitmask loop by a
loop only iterating over the bits set in the bitmask.

v2: Use _mesa_bit_scan{,64} instead of open coding.
v3: Use u_bit_scan{,64} instead of _mesa_bit_scan{,64}.

Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>
Signed-off-by: Mathias Fröhlich <f51464c0d83b5283880370f10770eaa83440cc6a@web.de>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler