Kernel: Remove various other uses of ssize_t

Author: https://github.com/gunnarbeutner
Commit: bc3076f894
Pull-request: https://github.com/SerenityOS/serenity/pull/8093
Reviewed-by: https://github.com/awesomekling

Kernel/FileSystem/DevPtsFS.cpp

@@ -100,12 +100,12 @@ DevPtsFSInode::~DevPtsFSInode()
 {
 }
 
-KResultOr<ssize_t> DevPtsFSInode::read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const
+KResultOr<size_t> DevPtsFSInode::read_bytes(off_t, size_t, UserOrKernelBuffer&, FileDescription*) const
 {
     VERIFY_NOT_REACHED();
 }
 
-KResultOr<ssize_t> DevPtsFSInode::write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*)
+KResultOr<size_t> DevPtsFSInode::write_bytes(off_t, size_t, const UserOrKernelBuffer&, FileDescription*)
 {
     VERIFY_NOT_REACHED();
 }