Tegra: spe: use CONSOLE_T_BASE to save MMIO base address

Commit ac71344e moved the base address
for the MMIO aperture of the console inside the console_t struct. As
a result, the driver should now save the MMIO base address to console_t
at offset marked by the CONSOLE_T_BASE macro.

This patch updates the SPE console driver to use the CONSOLE_T_BASE macro
to save/access the MMIO base address.

Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Change-Id: I42afc2608372687832932269108ed642f218fd40