mtd: nand: ecc-mxic: Fix use of uninitialized variable ret

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

mtd: nand: ecc-mxic: Fix use of uninitialized variable ret

If ctx->steps is zero, the loop processing ECC steps is skipped,

and the variable ret remains uninitialized. It is later checked

and returned, which leads to undefined behavior and may cause

unpredictable results in user space or kernel crashes.

This scenario can be triggered in edge cases such as misconfigured

geometry, ECC engine misuse, or if ctx->steps is not validated

after initialization.

Initialize ret to zero before the loop to ensure correct and safe

behavior regardless of the ctx->steps value.

Found by Linux Verification Center (linuxtesting.org) with SVACE.