MIPS: bcm63xx: nvram: Remove unused bcm63xx_nvram_get_psi_size() function

MIPS: bcm63xx: nvram: Remove unused bcm63xx_nvram_get_psi_size() function

Remove bcm63xx_nvram_get_psi_size() as it now has no users.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Jonas Gorski <jogo@openwrt.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc: MIPS Mailing List <linux-mips@linux-mips.org>
Cc: MTD Maling List <linux-mtd@lists.infradead.org>
Patchwork: https://patchwork.linux-mips.org/patch/11836/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>