doc: board: avoid ambiguous names for axy17lte

Model names are SM-A{3,5,7}20, just SM-{3,5,7}20 could also refer to
SM-J{3,5,7}20 or SM-T{3,5,7}20.

Fixes: 3e2095e960b4 ("board: samsung: add support for Galaxy A series
of 2017 (a5y17lte)")
Signed-off-by: Henrik Grimler <henrik@grimler.se>
Reviewed-by: Dzmitry Sankouski <dsankouski@gmail.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
diff --git a/doc/board/samsung/axy17lte.rst b/doc/board/samsung/axy17lte.rst
index 511cd57..4307e51 100644
--- a/doc/board/samsung/axy17lte.rst
+++ b/doc/board/samsung/axy17lte.rst
@@ -14,7 +14,7 @@
 
 Phone specs
 -----------
-A3 (SM-320) (a3y17lte)
+A3 (SM-A320) (a3y17lte)
 ^^^^^^^^^^^^^^^^^^^^^^
 - 4.7 AMOLED display
 - Exynos 7870 SoC
@@ -23,7 +23,7 @@
 
 .. A3 2017 wiki page: https://en.wikipedia.org/wiki/Samsung_Galaxy_A3_(2017)
 
-A5 (SM-520) (a5y17lte)
+A5 (SM-A520) (a5y17lte)
 ^^^^^^^^^^^^^^^^^^^^^^
 - 5.2 AMOLED display
 - Exynos 7880 SoC
@@ -32,7 +32,7 @@
 
 .. A5 2017 wiki page: https://en.wikipedia.org/wiki/Samsung_Galaxy_A5_(2017)
 
-A7 (SM-720) (a5y17lte)
+A7 (SM-A720) (a5y17lte)
 ^^^^^^^^^^^^^^^^^^^^^^
 - 5.7 AMOLED display
 - Exynos 7880 SoC