Documentation: w1: Fix SPDX comment syntax on masters and slaves toctree index

Commit e9bb627561535d ("docs: w1: convert to ReST and add to the kAPI
group of docs") converts 1-Wire docs to reST alongside with SPDX
comment, yet the comment is written in one dot as opposed to two in
order to be recognized as comment directive, which spills it into
htmldocs output. This issue is partially fixed in d8fb03e1ea64e7 ("docs:
w1: Fix SPDX-License-Identifier syntax") as it only touches top-level w1
toctree.

Do the same fix on masters and slaves toctrees.

Fixes: e9bb62756153 ("docs: w1: convert to ReST and add to the kAPI group of docs")
Signed-off-by: Bagas Sanjaya <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>
Message-ID: <[e-mail]>

Documentation/w1/masters/index.rst

···
-. SPDX-License-Identifier: GPL-2.0
+.. SPDX-License-Identifier: GPL-2.0
 
 =====================
 1-wire Master Drivers

Documentation/w1/slaves/index.rst

···
-. SPDX-License-Identifier: GPL-2.0
+.. SPDX-License-Identifier: GPL-2.0
 
 ====================
 1-wire Slave Drivers