Unify the types of two NumFrame variables and Code Optimization

1.For code portability and stability, it is recommended to define both variables as int32_t so that the sizes of the two variables are fixed regardless of the platform.
2.The two variables mNumAcquired and mNumFrameAvailable are initialized to 0 when declared in the header file. It is recommended to remove the re-initialization of these two values in the BBQ constructor of the source file.

Signed-off-by:
Shuangxi Xiang <xiangshuangxi@xiaomi.corp-partner.google.com>

Change-Id: I7cb525e62d1005b2a67cceb8e3efe0e3236506db