ARM: dts: aspeed: system1: Bump up i2c busses freq

Bump up i2c8 and i2c15 bus frequency so that PCIe slot and FPGA runs
faster

Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Link: https://patch.msgid.link/20241001191756.234096-2-ninad@linux.ibm.com


Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>