aemfvp-rme: update build-scripts for 23'q4 release

The 23'q4 release of aemfvp-rme software stack migrates the quality
level of the stack to EAC5. There are changes in scripts as part of this
migration and those are -

- update buildroot config file to 2023.08.
- GCC version updated to 12.3.rel1
- kvm bridge and interface creation scripts added.
- ssh_connection test added.
- applying kconf patch for disabling cpu idle at FVP.
- TF_A build flags updated.
- Hafnium build PLATFORM included.
- Buildroot.config file updated

Signed-off-by: Nitin Sharma <nitin.sharma3@arm.com>
Change-Id: I2fd19eb8e822e7550675bf12dfa56cb504b9f854