storagecommands: Extended I2C bus size to 16-bit

The entity-manager and phosphor-host-ipmid changed the D-Bus signature
of the I2C bus number variable from 8-bit to 16-bit.

This commit extented bus size to 16-bit to fix signature mismatch.

Signed-off-by: Potin Lai <potin.lai@quantatw.com>
Change-Id: I37d229bc19b59817ce39ac22d81ef8776feaf8cc
diff --git a/src/storagecommands.cpp b/src/storagecommands.cpp
index f99480d..d64531e 100644
--- a/src/storagecommands.cpp
+++ b/src/storagecommands.cpp
@@ -65,7 +65,7 @@
 constexpr static const size_t cacheTimeoutSeconds = 10;
 
 static std::vector<uint8_t> fruCache;
-static uint8_t cacheBus = 0xFF;
+static uint16_t cacheBus = 0xFFFF;
 static uint8_t cacheAddr = 0XFF;
 
 std::unique_ptr<phosphor::Timer> cacheTimer = nullptr;
@@ -314,7 +314,7 @@
     catch (const sdbusplus::exception_t&)
     {
         lastDevId = 0xFF;
-        cacheBus = 0xFF;
+        cacheBus = 0xFFFF;
         cacheAddr = 0xFF;
         return IPMI_CC_RESPONSE_ERROR;
     }