net: ipa: fix build-time bug in ipa_hardware_config_qsb()

net: ipa: fix build-time bug in ipa_hardware_config_qsb()

Jon Hunter reported observing a build bug in the IPA driver:
  https://lore.kernel.org/netdev/5b5d9d40-94d5-5dad-b861-fd9bef8260e2@nvidia.com

The problem is that the QMB0 max read value set for IPA v4.5 (16) is
too large to fit in the 4-bit field.

The actual value we want is 0, which requests that the hardware use
the maximum it is capable of.

Reported-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20201202141502.21265-1-elder@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>