media: s5p-jpeg: rename JPEG marker constants to prevent build warnings

The use of a macro named 'RST' conflicts with one of the same name
in arch/mips/include/asm/mach-rc32434/rb.h. This causes build
warnings on some MIPS builds.

Change the names of the JPEG marker constants to be in their own
namespace to fix these build warnings and to prevent other similar
problems in the future.

Fixes these build warnings:

In file included from ../drivers/media/platform/s5p-jpeg/jpeg-hw-exynos3250.c:14:
../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
   43 | #define RST                             0xd0
      |
../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
   13 | #define RST             (1 << 15)

In file included from ../drivers/media/platform/s5p-jpeg/jpeg-hw-s5p.c:13:
../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
   43 | #define RST                             0xd0
../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
   13 | #define RST             (1 << 15)

In file included from ../drivers/media/platform/s5p-jpeg/jpeg-hw-exynos4.c:12:
../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
   43 | #define RST                             0xd0
../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
   13 | #define RST             (1 << 15)

In file included from ../drivers/media/platform/s5p-jpeg/jpeg-core.c:31:
../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
   43 | #define RST                             0xd0
../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
   13 | #define RST             (1 << 15)

Also update the kernel-doc so that the word "marker" is not
repeated.

Link: https://lore.kernel.org/linux-media/20210907044022.30602-1-rdunlap@infradead.org
Fixes: bb677f3ac434 ("[media] Exynos4 JPEG codec v4l2 driver")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Andrzej Pietrasiewicz <andrzejtp2010@gmail.com>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>