Kernel/File: Fixed file read/write hwtests

The 3DS allows the user to read from files opened with the Write access modifier, even if he did not specify the Read access modifier.

Open the files in binary mode so that we can prevent CR/LF problems in Windows, where a line-end is replaced by these two bytes instead of just 0xA, this was causing problems with the GetSize .

Used https://gist.github.com/Subv/e98f5e2947fd25f86329 to verify the behavior, now it's identical in both Citra and Hardware
Please don’t add trailing whitespaces.