android: r600/sfn: fix sfn_nir_algebraic.c gen rules

android: r600/sfn: fix sfn_nir_algebraic.c gen rules

Changelog:
- Correct typo in generator name which is sfn_nir_algebraic.py
- Rename variables for the gen rules according to meson rules
- Align python command and options according to meson rules

Fixes the following building error:

FAILED: ninja: 'external/mesa/src/gallium/drivers/r600/sfn/r600_nir_algebraic.py',
needed by 'out/target/product/x86_64/gen/STATIC_LIBRARIES/libmesa_pipe_r600_intermediates/sfn_nir_algebraic.c',
missing and no known rule to make it

Fixes: 195952786b08 ("r600/sfn: Add algebraic lowering for fsin and fcos")
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9766>