ksmbd: fix buffer validation by including null terminator size in EA length

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix buffer validation by including null terminator size in EA length

The smb2_set_ea function, which handles Extended Attributes (EA),

was performing buffer validation checks that incorrectly omitted the size

of the null terminating character (+1 byte) for EA Name.

This patch fixes the issue by explicitly adding '+ 1' to EaNameLength where

the null terminator is expected to be present in the buffer, ensuring

the validation accurately reflects the total required buffer size.