firmware: tegra: Switch to global mrq_is_supported()

Patch "firmware: tegra: add helper to check for supported MRQs" added
an API to check if MRQ is supported. Remove the implementation from
bpmp debugfs code in favor of that.

Signed-off-by: Timo Alho <talho@nvidia.com>
Acked-by: Sivaram Nair <sivaramn@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>