LPC54608: Raise the core freq on LPC54608 targets

[mmahadevan108]

Description

Raise the core freq on LPC54608 targets, this is incorrectly set to a lower value

Pull request type

[ ] Fix
[X] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[mmahadevan108]

cc @0xc0170 @maclobdell @cmonr

[NirSonnenschein]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3422
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8486/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 3046
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8486/

[mbed-ci]

Test : SUCCESS

Build number : 3216
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8486/3216