msm: net: ecm: variable name change

The driver context was saved in a variable called "dev".
The use of "dev" causes a collision with the "struct device *dev"
contained in the network interface struct "struct net_device".
In this change the "dev" usage is replaced with "ecm_ipa_ctx".
The "ecm_ipa_ctx" parameter shall hold the driver context.

Change-Id: Ibbb66f1ffe32dce8603969994c8bf7d53db69b08
Signed-off-by: Talel Atias <tatias@codeaurora.org>