memory: omap-gpmc: remove unused file-scope phys_base and mem_size

memory: omap-gpmc: remove unused file-scope phys_base and mem_size

The file-scope variables phys_base and mem_size are assigned in
gpmc_probe() but never read.

This fixes build error when compile testing on x86_64 architecture:

    drivers/memory/omap-gpmc.c:246:24: error: conflicting types for ‘phys_base’
     static resource_size_t phys_base, mem_size;
    In file included from arch/x86/include/asm/page.h:12:0,
                     from arch/x86/include/asm/thread_info.h:12,
                     from include/linux/thread_info.h:38,
                     from arch/x86/include/asm/preempt.h:7,
                     from include/linux/preempt.h:78,
                     from include/linux/spinlock.h:51,
                     from include/linux/irq.h:14,
                     from drivers/memory/omap-gpmc.c:12:
    arch/x86/include/asm/page_64.h:12:22: note: previous declaration of ‘phys_base’ was here
     extern unsigned long phys_base;

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200724074038.5597-3-krzk@kernel.org