config: versal: Update mini u-boot timer clock to 100Mhz

Mini u-boot timer clock is not updated when u-boot is migrated from
emulator to silicon. Due to this slower clock of 2.72Mhz, delay() functions
are not working accurately. Update CONFIG_COUNTER_FREQUENCY to 100Mhz.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>