Rework use of interconnect drivers

Rework use of interconnect drivers

ARM Trusted Firmware supports 2 different interconnect peripheral
drivers: CCI and CCN. ARM platforms are implemented using either of the
interconnect peripherals.

This patch adds a layer of abstraction to help ARM platform ports to
choose the right interconnect driver and corresponding platform support.
This is as described below:

1. A set of ARM common functions have been implemented to initialise an
interconnect and for entering/exiting a cluster from coherency. These
functions are prefixed as "plat_arm_interconnect_". Weak definitions of
these functions have been provided for each type of driver.

2.`plat_print_interconnect_regs` macro used for printing CCI registers is
moved from a common arm_macros.S to cci_macros.S.

3. The `ARM_CONFIG_HAS_CCI` flag used in `arm_config_flags` structure
is renamed to `ARM_CONFIG_HAS_INTERCONNECT`.

Change-Id: I02f31184fbf79b784175892d5ce1161b65a0066c