usb: gadget: ffs: Remove IPC context create failure log

In the case CONFIG_IPC_LOGGING is not defined,
ipc_log_context_create() return NULL. Remove error log
about IPC context create failure to avoid confuse.

Change-Id: Ia03528400f3bc9719de2676820f5a676281181b0
Signed-off-by: Liangliang Lu <luliang@codeaurora.org>