libstagefright: refactor Legacy LPA makefile

  - add in msm7x27a
  - remove unused USE_LPA_MODE flag

Change-Id: I9e8d9376e1cfbd37e6457c0fd8e6252848f6b24d
libstagefright: Enable meta mode for 7x27a video encoder

msm7627a family of chipsets supports only one input frame at
one time. camera expects the input frame to be released before
sending another frame. so send one input buffer and available
output bufefrs to video encoder component. Release the input
buffer to camera (to get another frame) after receiving input
frame done callback from video encoder component.

Change-Id: I8fbc911f046ff7e2a3047dd65d8c09ac2d8608e2
libstagefright: Add support for custom LPA buffer size in legacy LPAPlayer

     - on msm7x27a with bootloader heap for lpa audio during audio playback with,
       DSP Manager effects enabled there is a lot of stuttering with the default buffer size.
       with bl heap we need buffer size of 480, but that breaks audio at in cm. So we have,
       to use buffer size of 512 to get audio working but it makes stuttering as mentioned.
       so add support for a custom buffer size so we can use 480 buffer size.

Change-Id: Ib4b5222b4b64d42288e0ad5c95910e385d172374