stagefright: add -P pixelformat flag for -t (thumbnail) option in stagefright

when -P is supplied the output is in raw format for thumbnail, and it gets
output to /sdcard/out.raw (instead of /sdcard/out.jpg)

Supported -P values:

-P 1 :: RGBA_8888 (R is first byte)
-P 4 :: RGBA_565
-P 5 :: BGRA_8888 (B is first byte)
-P 43 :: RGBA_1010102
-P -43 :: RGBA_1010102 saved as RGBA_8888
          (this mode is added because many tools don't support RGBA_1010102)

Use as:
  stagefright -t -P 4 <file>

Bug: 216707498
Change-Id: Ib3fa6f332427ad5148903fae0c93640a4861be41