soc: lpc55xxx: Fix system hw clock cycle rate

Commit c6e3bac4 changed the core clock frequency of LPC55XXX series.
That clock is used by the cortex-m systick timer, which is the
default timer used for system time in zephyr on this series.
The bug is that the config SYS_CLOCK_HW_CYCLES_PER_SEC default was not
updated on the affected platforms to account for this change, so system
time is currently recorded as 150% of reality. Fix this by changing the
kconfig to be set automatically at SOC level and remove board defaults.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>
(cherry picked from commit 4d654250)