telephony: Increase the MAX_CONNECTIONS to 8

The problem is that Telephony does not handle call id 2 for CDMA.
When back to back calls are made, RIL stores the previous call information
for some time as it needs to give failure reason for the last call
that failed when telephony asks for it.
So for the next call it assigns a call ID of 2.

Bug: 10355466
Change-Id: I9a4a188780bde9e66aacc7a43d54df1118b10dfb