doc: samsung: axy17lte: Fix underlines

A few sections had underlines that were too short, correct.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/doc/board/samsung/axy17lte.rst b/doc/board/samsung/axy17lte.rst
index 4307e51..e84fefe 100644
--- a/doc/board/samsung/axy17lte.rst
+++ b/doc/board/samsung/axy17lte.rst
@@ -15,7 +15,7 @@
 Phone specs
 -----------
 A3 (SM-A320) (a3y17lte)
-^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^
 - 4.7 AMOLED display
 - Exynos 7870 SoC
 - 16GB flash
@@ -24,7 +24,7 @@
 .. A3 2017 wiki page: https://en.wikipedia.org/wiki/Samsung_Galaxy_A3_(2017)
 
 A5 (SM-A520) (a5y17lte)
-^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^
 - 5.2 AMOLED display
 - Exynos 7880 SoC
 - 32GB flash
@@ -33,7 +33,7 @@
 .. A5 2017 wiki page: https://en.wikipedia.org/wiki/Samsung_Galaxy_A5_(2017)
 
 A7 (SM-A720) (a5y17lte)
-^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^
 - 5.7 AMOLED display
 - Exynos 7880 SoC
 - 32GB flash