Using right type to get return value of As32Bit

Refer to the function As32Bit, we know that the return
value type is 32 bit integer. So we should use uint32_t
type there. Since we will treat it as a 32 bit number at
below code lines.

Test: No steps, just code refine
Fixes: 284210757
Change-Id: Ic578d41ae80ec6a254a42759341dcd115cf67abf