PCI: mobiveil: Unify register accessors

It is confusing to have two sets of functions to read/write
registers, some with csr_readl()/csr_writel(), while others with
read_paged_register()/write_paged_register().

In the register space the lower 3KB of 4KB PCIe configure space can be
accessed directly and higher 1KB through a simple paging mechanism.

Unify the register accessors in csr_readl() and csr_writel() by
comparing the register offset with page access boundary 3KB in the
accessor internal so that the paging mechanism is hidden behind
the csr_read()/write() common function calls.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Reviewed-by: Subrahmanya Lingappa <l.subrahmanya@mobiveil.co.in>