sf: Add RGBA_4444 and RGBA_5551 format in getFormatStr function

Add RGBA_4444 and RGBA_5551 format in getFormatStr function to log
string name instead of format number in dumpsys Surfaceflinger log.

Change-Id: Ib8423f27ce6bc0fd1b99e7610a870b39ff6441c0
sf: Rename default app buffer count property

We are setting default app buffer count property from HAL,
and there we can't go with read only based property.
Hence renaming it.

Change-Id: I9fd4bdb50aca35647402c59b24d78ad5f878aab5