Documentation: proc.txt: Adding 'HardwareCorrupted' field and description.

Fill in missing documentation for the HardwareCorrupted field in proc.txt.
Signed-off-by: NPrashant Dhamdhere <pdhamdhe@redhat.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/filesystems/proc.txt

@@ -870,6 +870,7 @@ Committed_AS:   100056 kB
 VmallocTotal:   112216 kB
 VmallocUsed:       428 kB
 VmallocChunk:   111088 kB
+HardwareCorrupted:   0 kB
 AnonHugePages:   49152 kB
 ShmemHugePages:      0 kB
 ShmemPmdMapped:      0 kB
@@ -915,6 +916,8 @@ MemAvailable: An estimate of how much memory is available for starting new
        Dirty: Memory which is waiting to get written back to the disk
    Writeback: Memory which is actively being written back to the disk
    AnonPages: Non-file backed pages mapped into userspace page tables
+HardwareCorrupted: The amount of RAM/memory in KB, the kernel identifies as
+	      corrupted.
 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
       Mapped: files which have been mmaped, such as libraries
        Shmem: Total memory used by shared memory (shmem) and tmpfs