ramips: backport upstream mt762x PCIe driver error log fixes

ramips: backport upstream mt762x PCIe driver error log fixes

These patches silence some mt762x PCIe driver error messeges by removing
the useless debugging codes and replacing incorrectly used 'dev_err()'
with 'dev_info()':

PCI: mt7621: Use dev_info() to log PCIe card detection [1]
mips: pci-mt7620: do not print NFTS register value as error log [2]
mips: pci-mt7620: use dev_info() to log PCIe device detection result [3]

Patch [1] has already been merged into the Linux 6.3 branch. Patches [2] and
[3] have been merged into the "mips-next" tree, and they will be part of the
upcoming Linux 6.5.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.4-rc7&id=50233e105a0332ec0f3bc83180c416e6b200471e
[2] https://git.kernel.org/pub/scm/linux/kernel/git/mips/linux.git/commit/?id=9f9a035e6156a57d9da062b26d2a48d031744a1e
[3] https://git.kernel.org/pub/scm/linux/kernel/git/mips/linux.git/commit/?id=89ec9bbe60b61cc6ae3eddd6d4f43e128f8a88de

Signed-off-by: Shiji Yang <yangshiji66@qq.com>
(cherry picked from commit 4e74777fa8111a2bdf63164a4920a42917faec28)