UPSTREAM: firmware: tegra: Fix error application of sizeof() to pointer

Application of sizeof() to pointer yields the number of bytes of the
pointer, but it should use the length of buffer in the code.

Bug: 254441685
Fixes: 06c2d9a0 ("firmware: tegra: Reduce stack usage")
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Lv Ruyi <lv.ruyi@zte.com.cn>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
(cherry picked from commit 711e26c0)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ide1f9cbc31fea6fbb1d74f7ad4bbb6bef7caa0a9