i2c: tegra-bpmp: don't modify input variable in xlate_flags

Since commit bc1c2048

 ("i2c: bpmp-tegra: Ignore unknown I2C_M
flags") we don't need to mask out flags and can keep the input variable
as is to save quite some lines.

Signed-off-by: Wolfram Sang <wsa@kernel.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>