Documentation: drop optional BOMs

A few of the Documentation .rst files begin with a Unicode
byte order mark (BOM). The BOM may signify endianess for
16-bit or 32-bit encodings or indicate that the text stream
is indeed Unicode. We don't need it for either of those uses.
It may also interfere with (confuse) some software.

Since we don't need it and its use is optional, just delete
the uses of it in Documentation/.

https://en.wikipedia.org/wiki/Byte_order_markSigned-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Link: https://lore.kernel.org/r/20210506231907.14359-1-rdunlap@infradead.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/block/data-integrity.rst

-==============
+==============
 Data Integrity
 ==============
 

Documentation/process/kernel-enforcement-statement.rst

-.. _process_statement_kernel:
+.. _process_statement_kernel:
 
 Linux Kernel Enforcement Statement
 ----------------------------------

Documentation/security/tpm/xen-tpmfront.rst

-=============================
+=============================
 Virtual TPM interface for Xen
 =============================
 

Documentation/timers/no_hz.rst

-======================================
+======================================
 NO_HZ: Reducing Scheduling-Clock Ticks
 ======================================
 

Documentation/usb/mtouchusb.rst

-================
+================
 mtouchusb driver
 ================
 

Documentation/usb/usb-serial.rst

-==========
+==========
 USB serial
 ==========