sccb-ng: fix off-by-one device capacity check to prevent overflow

[RubenKelevra]

Description

SCCB_Install_Device() rejected new devices only when device_count > MAX_DEVICES. When device_count == MAX_DEVICES the function still proceeded to install the device and wrote to devices[device_count], i.e. devices[MAX_DEVICES], which is one element past the end of the devices[] array (valid indices 0..MAX_DEVICES-1).

This off-by-one results in a buffer overflow / write outside the designated memory area and then increments device_count to MAX_DEVICES+1.

Change the guard to device_count >= MAX_DEVICES so we refuse installation once the array is full and prevent the out-of-bounds write/read chain.

Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.