Modify to properly use unsigned offset for fseek

Modify to properly use unsigned offset for fseek

The fseek gets second parameter(offset) as long type. Since the size of
the long type is different depends on the architecture(32/64-bits), any
offset value which type is greater than long should be treated with
care.
To resolve this issue, fseek_offset_u64 function is created and used.
Also, offset values which are used in fseek_offset_u64 are re-typed
properly.

Change-Id: Ic213744ad866a8d4533a8016d59c96703eecc226
Signed-off-by: SangYoun Kwak <sy.kwak@samsung.com>