I get the message "amdgpu 0000:01:00.0: Invalid PCI ROM header signature:
expecting 0xaa55, got 0xffff" during boot. This message interrupt the graphicl
boot. Also some times my computer gets froozen during boot and stop respond to
keybaord key press and I have to do a hard reset.

I have tested with other distro (Solus) without this issue and they are on the
same kernel tree (4.14.x)

sudo lspci | grep VGA
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
Ellesmere [Radeon RX 470/480/570/580] (rev c7)

uname -a
Linux jarvis 4.14.9-1-default #1 SMP PREEMPT Mon Dec 25 15:42:48 UTC 2017
(9423ca2) x86_64 x86_64 x86_64 GNU/Linux

lsb_release -a
LSB Version:    n/a
Distributor ID:    openSUSE
Description:    openSUSE Tumbleweed
Release:    20171231
Codename:    n/a

found below from arch linux wiki:

Also, since kernel 4.13, adding the amdgpu.si_support=1 radeon.si_support=0 or
amdgpu.cik_support=1 radeon.cik_support=0 kernel parameter is required.
Otherwise, AMDGPU will not start and you will end up with either radeon being
used instead or the display being frozen during the boot.

ref: https://wiki.archlinux.org/index.php/AMDGPU

Sounds alot like my issues.