ARM: 5785/1: Use ST vendor enum instead of numeral

This fixes a leftover instance of using the 0x80 numeral instead
of the new AMBA_VENDOR_ST enum in the MMCI/PL180 driver.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>