CVE-2023-54295

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

mtd: spi-nor: Fix shift-out-of-bounds in spinorseterasetype

spinorseterasetype() was used either to set or to mask out an erase type. When we used it to mask out an erase type a shift-out-of-bounds was hit: UBSAN: shift-out-of-bounds in drivers/mtd/spi-nor/core.c:2237:24 shift exponent 4294967295 is too large for 32-bit type 'int'

The setting of the size_{shift, mask} and of the opcode are unnecessary when the erase size is zero, as throughout the code just the erase size is considered to determine whether an erase type is supported or not. Setting the opcode to 0xFF was wrong too as nobody guarantees that 0xFF is an unused opcode. Thus when masking out an erase type, just set the erase size to zero. This will fix the shift-out-of-bounds.

[ta: refine changes, new commit message, fix compilation error]