firmware_loader: Strip off \n from customized path

firmware_loader: Strip off \n from customized path

Having helped an user recently figure out why the customized path being
specified was not taken into account landed on a subtle difference
between using:

echo "/xyz/firmware" > /sys/module/firmware_class/parameters/path

which inserts an additional newline which is passed as is down to
fw_get_filesystem_firmware() and ultimately kernel_read_file_from_path()
and fails.

Strip off \n from the customized firmware path such that users do not
run into these hard to debug situations.

Link: https://lore.kernel.org/all/20230402135423.3235-1-f.fainelli@gmail.com/
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230413191757.1949088-1-f.fainelli@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>