fastboot: Remove "slot-suffixes" variable

"slot-suffixes" variable was dropped in fastboot tool (in [1]). Let's
track AOSP/master and drop this variable in U-Boot as well.

[1] https://android.googlesource.com/platform/system/core/+/42b18a518bac85c3eea14206f6cbafbd1e98a31f

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
[lukma: Remove getvar_slot_suffixes() declaration]
Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/drivers/fastboot/fb_getvar.c b/drivers/fastboot/fb_getvar.c
index bf957e8..9ee5054 100644
--- a/drivers/fastboot/fb_getvar.c
+++ b/drivers/fastboot/fb_getvar.c
@@ -19,7 +19,6 @@
 static void getvar_product(char *var_parameter, char *response);
 static void getvar_platform(char *var_parameter, char *response);
 static void getvar_current_slot(char *var_parameter, char *response);
-static void getvar_slot_suffixes(char *var_parameter, char *response);
 #if CONFIG_IS_ENABLED(FASTBOOT_FLASH)
 static void getvar_has_slot(char *var_parameter, char *response);
 #endif
@@ -64,9 +63,6 @@
 	}, {
 		.variable = "current-slot",
 		.dispatch = getvar_current_slot
-	}, {
-		.variable = "slot-suffixes",
-		.dispatch = getvar_slot_suffixes
 #if CONFIG_IS_ENABLED(FASTBOOT_FLASH)
 	}, {
 		.variable = "has-slot",
@@ -182,11 +178,6 @@
 	fastboot_okay("a", response);
 }
 
-static void getvar_slot_suffixes(char *var_parameter, char *response)
-{
-	fastboot_okay("a,b", response);
-}
-
 #if CONFIG_IS_ENABLED(FASTBOOT_FLASH)
 static void getvar_has_slot(char *part_name, char *response)
 {