[ARM] 5176/1: arm/Makefile: fix: ARM946T -> ARM946E

This patch fixes a typo introduced by
commit f37f46eb
([ARM] nommu: add ARM946E-S core support).

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Hyok S. Choi <hyok.choi@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>