net: systemport: Remove unused txchk accessors

Vladimir reported the following warning with clang-16 and W=1:

warning: unused function 'txchk_readl' [-Wunused-function]
BCM_SYSPORT_IO_MACRO(txchk, SYS_PORT_TXCHK_OFFSET);
note: expanded from macro 'BCM_SYSPORT_IO_MACRO'

warning: unused function 'txchk_writel' [-Wunused-function]
note: expanded from macro 'BCM_SYSPORT_IO_MACRO'

warning: unused function 'tbuf_readl' [-Wunused-function]
BCM_SYSPORT_IO_MACRO(tbuf, SYS_PORT_TBUF_OFFSET);
note: expanded from macro 'BCM_SYSPORT_IO_MACRO'

warning: unused function 'tbuf_writel' [-Wunused-function]
note: expanded from macro 'BCM_SYSPORT_IO_MACRO'

The TXCHK and RBUF blocks are not being accessed, remove the IO macros
used to access those blocks. No functional impact.

Reported-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241021174935.57658-2-florian.fainelli@broadcom.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>