toolchain/binutils: completely remove 2.28 support

Commit 15e963915963cda515311531b182b9e0c52f35a0 removed support for
binutils version 2.28 but did not remove it as selectable item
from Binutils Version; let's remove this leftover as well.

Signed-off-by: Hans Dedecker <[email protected]>

toolchain/binutils/Config.in

@@ -12,11 +12,6 @@ choice
 		bool "Binutils 2.27"
 		select BINUTILS_VERSION_2_27
 
-	config BINUTILS_USE_VERSION_2_28
-		depends on !arc
-		bool "Binutils 2.28"
-		select BINUTILS_VERSION_2_28
-
 	config BINUTILS_USE_VERSION_2_29_ARC
 		depends on arc
 		bool "ARC binutils 2.29"