nuplayer: fix audioFormat error in offload mode

For audio with PCM_FLOAT and audio/raw，
Nuplayer uses incorrect audio format to determine if offload is supported.

bug:377433161

Change-Id: I6966a49706365076bcbe78876ecd07743d97298a
Signed-off-by: Aiguo <aiguo.feng@amlogic.corp-partner.google.com>