i965/vs: Don't lose attribute type when converting ATTR to FIXED_HW_REG.

i965/vs: Don't lose attribute type when converting ATTR to FIXED_HW_REG.

The new brw_reg always had type BRW_REGISTER_TYPE_F, rather than
inheriting the original type of the ATTR file register.

In the past, this hasn't been a problem since we only execute this code
when fixing up GL_FIXED attributes, which always have float types.
However, we'll soon be using it for ARB_vertex_type_10_10_10_2 support,
which uses D and UD types.

Reviewed-by: Eric Anholt <eric@anholt.net>