meta-facebook: fix up new shellcheck warnings

New docker container is flagging some issues in this shell script:

```
SC2004 (style): $/${} is unnecessary on arithmetic variables.
SC2317 (info): Command appears to be unreachable. Check usage (or ignore if invoked indirectly).
```

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I9806a097ca417d8677374efd666f2a8865a0a2fd
diff --git a/meta-facebook/meta-bletchley/recipes-phosphor/sensors/phosphor-nvme/nvme-json-rewrite b/meta-facebook/meta-bletchley/recipes-phosphor/sensors/phosphor-nvme/nvme-json-rewrite
index d30ed89..46d72f4 100644
--- a/meta-facebook/meta-bletchley/recipes-phosphor/sensors/phosphor-nvme/nvme-json-rewrite
+++ b/meta-facebook/meta-bletchley/recipes-phosphor/sensors/phosphor-nvme/nvme-json-rewrite
@@ -10,13 +10,13 @@
 
 for i in {0..5}
 do
-    SLED_NVME_PCIE_EN[$i]=0
+    SLED_NVME_PCIE_EN[i]=0
     for file in /sys/bus/i2c/drivers/pca953x/"$i"-0041/gpio/gpiochip*/base
     do
         if [ -f "$file" ]; then
             GPIOCHIP_BASE="$(cat /sys/bus/i2c/drivers/pca953x/"$i"-0041/gpio/gpiochip*/base)"
-            SLED_NVME_PCIE_EN[$i]=$((GPIOCHIP_BASE+3))
-            export_gpio ${SLED_NVME_PCIE_EN[$i]}
+            SLED_NVME_PCIE_EN[i]=$((GPIOCHIP_BASE+3))
+            export_gpio "${SLED_NVME_PCIE_EN[i]}"
             break
         fi
     done