nv30: provide a minimum map buffer alignment
nv30: provide a minimum map buffer alignment

Otherwise we return 0, which is out of spec. Return 64 like all the
other nouveau drivers.

Signed-off-by: Ilia Mirkin <bcbbb7aa705ec3a5fc5824c01a845186c3d62fca@alum.mit.edu>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler