arm_mpam: Add workaround for T241-MPAM-6

The registers MSMON_MBWU_L and MSMON_MBWU return the number of
requests rather than the number of bytes transferred.

Bandwidth resource monitoring is performed at the last level cache,
where each request arrive in 64Byte granularity. The current
implementation returns the number of transactions received at the
last level cache but does not provide the value in bytes. Scaling
by 64 gives an accurate byte count to match the MPAM specification
for the MSMON_MBWU and MSMON_MBWU_L registers. This patch fixes
the issue by reporting the actual number of bytes instead of the
number of transactions from __ris_msmon_read().

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Signed-off-by: James Morse <james.morse@arm.com>