can: rcar_canfd: Add missing ECC error checks for channels 2-7

When introducing support for R-Car V3U, which has 8 instead of 2
channels, the ECC error bitmask was extended to take into account the
extra channels, but rcar_canfd_global_error() was not updated to act
upon the extra bits.

Replace the RCANFD_GERFL_EEF[01] macros by a new macro that takes the
channel number, fixing R-Car V3U while simplifying the code.

Fixes: 45721c40

 ("can: rcar_canfd: Add support for r8a779a0 SoC")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/all/4edb2ea46cc64d0532a08a924179827481e14b4f.1666951503.git.geert+renesas@glider.be
Cc: stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>