mtd: cfi: Zap CFI_FLASH_SHIFT_WIDTH redefinition

This is defined twice in the same file, with the same value, likely
because of some patch merge issue. Pick the uglier one and nuke it.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Tom Rini <trini@konsulko.com>
Signed-off-by: Stefan Roese <sr@denx.de>