rust: cpufreq: Fix temporary write in Registration::bios_limit_callback

In `Registration::bios_limit_callback`, the expression
`&mut (unsafe { *limit })` creates a reference to a temporary copy
of the value pointed to by `limit` on the stack.
Therefore, writes made by `T::bios_limit` go to this temporary
instead of the memory location pointed to by `limit`.

Additionally, `limit` may be uninitialized, such as when
`Registration::bios_limit_callback` is invoked by `show_bios_limit`
in drivers/cpufreq/cpufreq.c. Therefore creating a reference to
`limit` is unsound.

Fix this by changing the signature of `T::bios_limit` to return the limit
value.
`Registration::bios_limit_callback` can then update `limit` directly.

Fixes: c6af9a1191d042839e56abff69e8b0302d117988 ("rust: cpufreq: Extend abstractions for driver registration")
Reported-by: Dylan Zueck<dzueck@uci.edu>
Reported-by: Yuan Tan<ytan089@ucr.edu>
Assisted-by: ChatGPT:gpt-5.4
Signed-off-by: Priya Bala Govindasamy<pgovind2@uci.edu>
[ Viresh: Fix rustfmtcheck warning ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

0 files changed, 0 insertions, 0 deletions