Fix Yaesu gran_parm

https://github.com/Hamlib/Hamlib/issues/1357

rigs/yaesu/frg100.c

@@ -174,7 +174,7 @@ const struct rig_caps frg100_caps =
     .has_get_level =      RIG_LEVEL_RAWSTR,
     .has_set_level =      RIG_LEVEL_BAND_SELECT,
     .has_get_parm =       RIG_PARM_NONE,
-    .has_set_parm =       RIG_PARM_BACKLIGHT,
+    .has_set_parm =       RIG_PARM_NONE,
     .level_gran =
     {
 #include "level_gran_yaesu.h"

rigs/yaesu/ft1000d.c

@@ -296,6 +296,9 @@ const struct rig_caps ft1000d_caps =
     {
 #include "level_gran_yaesu.h"
     },
+    .parm_gran =  {
+        [PARM_BACKLIGHT] = {.min = {.f = 0.0f}, .max = {.f = 1.0f}, .step = {.f = 1.0f / 13.0f}},
+    },
     .ctcss_list =         NULL,
     .dcs_list =           NULL,
     .preamp =             { RIG_DBLST_END, },

rigs/yaesu/ft990.c

@@ -263,6 +263,10 @@ const struct rig_caps ft990_caps =
     {
 #include "level_gran_yaesu.h"
     },
+    .parm_gran =  {
+        [PARM_BACKLIGHT] = {.min = {.f = 0.0f}, .max = {.f = 1.0f}, .step = {.f = 1.0f / 255.0f}},
+    },
+
     .ctcss_list =         NULL,
     .dcs_list =           NULL,
     .preamp =             { RIG_DBLST_END, },

rigs/yaesu/ft990v12.c

@@ -278,6 +278,10 @@ const struct rig_caps ft990uni_caps =
     .has_set_level =      RIG_LEVEL_BAND_SELECT,
     .has_get_parm =       RIG_PARM_NONE,
     .has_set_parm =       RIG_PARM_BACKLIGHT,
+    .parm_gran =  {
+        [PARM_BACKLIGHT] = {.min = {.f = 0.0f}, .max = {.f = 1.0f}, .step = {.f = 1.0f / 13.0f}},
+    },
+
     .ctcss_list =         NULL,
     .dcs_list =           NULL,
     .preamp =             { RIG_DBLST_END, },