Kobo: Yet another attempt at working around the hangs on the latest NXP boards (#10771)

* Notification: Drop the fencing from #10083; it never actually helped, and had subtle side-effects we could do without.
* VirtualKeyBoard: Flash on close, otherwise, some of the fast refresh glitches may be burned into the working buffer until a flash. Making sure we flash ourselves prevent it from sticking around on the page ;).
* util: Move `writeToSysfs` to base (i.e., `ffi/util`), as we need it there (and it actually makes more sense there anyway ;p).
* Bump base for https://github.com/koreader/koreader-base/pull/1645, which is where the actual workaround (hopefully) lives.

Re #8414, #9806, #10558

frontend/util.lua

@@ -5,13 +5,9 @@ This module contains miscellaneous helper functions for the KOReader frontend.
 local BaseUtil = require("ffi/util")
 local Utf8Proc = require("ffi/utf8proc")
 local lfs = require("libs/libkoreader-lfs")
-local logger = require("logger")
 local _ = require("gettext")
 local C_ = _.pgettext
 local T = BaseUtil.template
-local ffi = require("ffi")
-local C = ffi.C
-require("ffi/posix_h")
 
 local lshift = bit.lshift
 local rshift = bit.rshift
@@ -833,26 +829,6 @@ function util.removeFile(file)
     end
 end
 
-function util.writeToSysfs(val, file)
-    -- NOTE: We do things by hand via ffi, because io.write uses fwrite,
-    --       which isn't a great fit for procfs/sysfs (e.g., we lose failure cases like EBUSY,
-    --       as it only reports failures to write to the *stream*, not to the disk/file!).
-    local fd = C.open(file, bit.bor(C.O_WRONLY, C.O_CLOEXEC)) -- procfs/sysfs, we shouldn't need O_TRUNC
-    if fd == -1 then
-        logger.err("Cannot open file `" .. file .. "`:", ffi.string(C.strerror(ffi.errno())))
-        return
-    end
-    val = tostring(val)
-    local bytes = #val
-    local nw = C.write(fd, val, bytes)
-    if nw == -1 then
-        logger.err("Cannot write `" .. val .. "` to file `" .. file .. "`:", ffi.string(C.strerror(ffi.errno())))
-    end
-    C.close(fd)
-    -- NOTE: Allows the caller to possibly handle short writes (not that these should ever happen here).
-    return nw == bytes
-end
-
 -- Gets total, used and available bytes for the mountpoint that holds a given directory.
 -- @string path of the directory
 -- @treturn table with total, used and available bytes