usb: misc: qcom_eud: Access EUD_MODE_MANAGER2 through secure calls

EUD_MODE_MANAGER2 register is mapped to a memory region that is marked
as read-only for operating system running at EL1, enforcing access
restrictions that prohibit direct memory-mapped writes via writel().

Attempts to write to this region from HLOS can result in silent failures
or memory access violations, particularly when toggling EUD (Embedded
USB Debugger) state. To ensure secure register access, modify the driver
to use qcom_scm_io_writel(), which routes the write operation to Qualcomm
Secure Channel Monitor (SCM). SCM has the necessary permissions to access
protected memory regions, enabling reliable control over EUD state.

SC7280, the only user of EUD is also affected, indicating that this could
never have worked on a properly fused device.

Fixes: 9a1bf58c ("usb: misc: eud: Add driver support for Embedded USB Debugger(EUD)")
Signed-off-by: Melody Olvera <quic_molvera@quicinc.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Souradeep Chowdhury <quic_schowdhu@quicinc.com>
Signed-off-by: Komal Bajaj <komal.bajaj@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250731-eud_mode_manager_secure_access-v8-1-4a5dcbb79f41@oss.qualcomm.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>