arm_mpam: Add workaround for T241-MPAM-4

In the T241 implementation of memory-bandwidth partitioning, in the
absence of contention for bandwidth, the minimum bandwidth setting
can affect the amount of achieved bandwidth. Specifically, the
achieved bandwidth in the absence of contention can settle to any
value between the values of MPAMCFG_MBW_MIN and MPAMCFG_MBW_MAX.
Also, if MPAMCFG_MBW_MIN is set zero (below 0.78125%), once a core
enters a throttled state, it will never leave that state.

The first issue is not a cocern if the MPAM software allows to
program MPAMCFG_MBW_MIN through the sysfs interface. This patch
ensures program MBW_MIN=1 (0.78125%) whenever MPAMCFG_MBW_MIN=0
is programmed.

In the scenario where the resctrl doesn't support the MBW_MIN
interface via sysfs, to achieve bandwidth closer to MW_MAX in the
absence of contention, software should configure a relatively narrow
gap between MBW_MIN and MBW_MAX. The recommendation is to use a 5%
gap to mitigate the problem.

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
[ morse: Added as second quirk, adapted to use the new intermediate values
  in mpam_extend_config() ]
Signed-off-by: James Morse <james.morse@arm.com>