x86/sgx: Fix deadlock in SGX NUMA node search

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

x86/sgx: Fix deadlock in SGX NUMA node search

When the current node doesn't have an EPC section configured by firmware

and all other EPC sections are used up, CPU can get stuck inside the

while loop that looks for an available EPC page from remote nodes

indefinitely, leading to a soft lockup. Note how nid_of_current will

never be equal to nid in that while loop because nid_of_current is not

set in sgx_numa_mask.

Also worth mentioning is that it's perfectly fine for the firmware not

to setup an EPC section on a node. While setting up an EPC section on

each node can enhance performance, it is not a requirement for

functionality.

Rework the loop to start and end on *a* node that has SGX memory. This

avoids the deadlock looking for the current SGX-lacking node to show up

in the loop when it never will.