microblaze: Remove gcc flag for non existing early_printk.c file

microblaze: Remove gcc flag for non existing early_printk.c file

[ Upstream commit edc66cf0c4164aa3daf6cc55e970bb94383a6a57 ]

early_printk support for removed long time ago but compilation flag for
ftrace still points to already removed file that's why remove that line
too.

Fixes: 96f0e6fcc9ad ("microblaze: remove redundant early_printk support")
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/5493467419cd2510a32854e2807bcd263de981a0.1712823702.git.michal.simek@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>