idmap: Use local long variable to get the crc value from zip.

As the size of the long is 8 on the 64bit system and it is different from
the uint32_t as it's size is 4. So we need use a local variable of long to
get the crc value from the zip file.

Change-Id: I033251dac0b9478b638e5d68733d74f2fc2f4d8a