libstagefright: fix AV sync late margin on non-QCOM_HARDWARE

Change I65cd3dce9b31b87f1488c37af9618669b29c362c changed the
late margin to a property defaulting to the same 40ms as the
original code, but uses QCOM_HARDWARE dependencies to read
the value (otherwise it's left unset).

Hardwire it back as the default 40ms

Change-Id: If63e171ea4e9693aa90dd7fabd8997f361a3959c
libstagefright: unbreak hardware OMX on OMAP3

http://review.cyanogenmod.org/58070 has mistakenly reverted
http://review.cyanogenmod.org/44365 which broke hardware OMX
on OMAP3.

The fix for OMAP3 was just a logic change to prevent an
indefinate loop since the nIndex value was being overriden by
the OMX component. The code was modified to use a seprate control
value other than nIndex itself and doesnt pose any issues with
other platforms.

Change-Id: I8ca4f9d48c3f9241f21c9fe6ab98d0be5783ceab