ARM: davinci: da850-evm: Avoid NULL pointer dereference

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

ARM: davinci: da850-evm: Avoid NULL pointer dereference

With newer versions of GCC, there is a panic in da850_evm_config_emac()

when booting multi_v5_defconfig in QEMU under the palmetto-bmc machine:

Unable to handle kernel NULL pointer dereference at virtual address 00000020

pgd = (ptrval)

[00000020] *pgd=00000000

Internal error: Oops: 5 [#1] PREEMPT ARM

Modules linked in:

CPU: 0 PID: 1 Comm: swapper Not tainted 5.15.0 #1

Hardware name: Generic DT based system

PC is at da850_evm_config_emac+0x1c/0x120

LR is at do_one_initcall+0x50/0x1e0

The emac_pdata pointer in soc_info is NULL because davinci_soc_info only

gets populated on davinci machines but da850_evm_config_emac() is called

on all machines via device_initcall().

Move the rmii_en assignment below the machine check so that it is only

dereferenced when running on a supported SoC.