android: panfrost: Rename encoder/ to lib/

Fixes the following building errors:

target  C: libpanfrost_encoder <= external/mesa/src/panfrost/encoder/pan_attributes.c
...
clang: error: no such file or directory: 'external/mesa/src/panfrost/encoder/pan_attributes.c'
clang: error: no input files

target  C: libpanfrost_encoder <= external/mesa/src/panfrost/encoder/pan_afbc.c
...
clang: error: no such file or directory: 'external/mesa/src/panfrost/encoder/pan_afbc.c'
clang: error: no input files

Fixes: 1c62b5528 ("panfrost: Rename encoder/ to lib/")
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6261>