i2c: tegra-bpmp: Demote kernel-doc abuses

Fixes the following W=1 kernel build warning(s):

 drivers/i2c/busses/i2c-tegra-bpmp.c:86: warning: Function parameter or member 'i2c' not described in 'tegra_bpmp_serialize_i2c_msg'
 drivers/i2c/busses/i2c-tegra-bpmp.c:86: warning: Function parameter or member 'request' not described in 'tegra_bpmp_serialize_i2c_msg'
 drivers/i2c/busses/i2c-tegra-bpmp.c:86: warning: Function parameter or member 'msgs' not described in 'tegra_bpmp_serialize_i2c_msg'
 drivers/i2c/busses/i2c-tegra-bpmp.c:86: warning: Function parameter or member 'num' not described in 'tegra_bpmp_serialize_i2c_msg'
 drivers/i2c/busses/i2c-tegra-bpmp.c:86: warning: expecting prototype for The serialized I2C format is simply the following(). Prototype was for tegra_bpmp_serialize_i2c_msg() instead
 drivers/i2c/busses/i2c-tegra-bpmp.c:130: warning: Function parameter or member 'i2c' not described in 'tegra_bpmp_i2c_deserialize'
 drivers/i2c/busses/i2c-tegra-bpmp.c:130: warning: Function parameter or member 'response' not described in 'tegra_bpmp_i2c_deserialize'
 drivers/i2c/busses/i2c-tegra-bpmp.c:130: warning: Function parameter or member 'msgs' not described in 'tegra_bpmp_i2c_deserialize'
 drivers/i2c/busses/i2c-tegra-bpmp.c:130: warning: Function parameter or member 'num' not described in 'tegra_bpmp_i2c_deserialize'
 drivers/i2c/busses/i2c-tegra-bpmp.c:130: warning: expecting prototype for The data in the BPMP(). Prototype was for tegra_bpmp_i2c_deserialize() instead

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>