iosys-map: Rename locals used inside macros

Widely used variable names can be used by macro users, potentially
leading to name collisions.
Suffix locals used inside the macros with an underscore, to reduce the
collision potential.

Suggested-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231024110710.3039807-1-michal.winiarski@intel.com