ARM: tegra: Remove gratuitous parentheses in SPDX license identifier

Parentheses in the SPDX license identifier are only used to group sub-
expressions. If there's no need for such grouping, the parentheses can
be omitted.

Reviewed-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>