ARM: dts: msm: Set default gadget IMOD value to 250us for SA415M USB EP

Set parameter "qcom,gadget-imod-val" to 250 for SA415M USB EP
targets (USB interconnect). This is required to optimize CPU usage
since there is a single core on SA415.

Change-Id: I2523289aab551ffae0f8301ecd96653cfc65d215
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>