Fix GPS Buffer full issue on NRF52480 (Seeed T1000E) (#8956)

We set the buffer size to about a byte on NRF52480, less than
other platforms:

esp32.ini:  -DSERIAL_BUFFER_SIZE=4096
esp32c6.ini:  -DSERIAL_BUFFER_SIZE=4096
nrf52.ini:  -DSERIAL_BUFFER_SIZE=1024

However, 115200 baud, like the T1000e uses is about 12 times that
- almost 15 bytes per millisecond.
15 bytes * 200 millisecond (our GPS poll rate)  = 3000 bytes, which is longer than our buffer
on the nrf52 platform. This causes "GPS Buffer full" errors on the T1000e
and other devices based on NRF52480 with newer GPS chips.

This patch increases SERIAL_BUFFER_SIZE for nrf52480 to 4096 to align with
other platforms. It keeps the original 1024 for the nrf52832, which has
fewer resources.

Fixes https://github.com/meshtastic/firmware/issues/5767

variants/nrf52840/nrf52.ini

@@ -19,7 +19,6 @@ build_type = release
 build_flags =
   -include variants/nrf52840/cpp_overrides/lfs_util.h
   ${arduino_base.build_flags}
-  -DSERIAL_BUFFER_SIZE=1024
   -Wno-unused-variable
   -Isrc/platform/nrf52
   -DLFS_NO_ASSERT                      ; Disable LFS assertions , see https://github.com/meshtastic/firmware/pull/3818

variants/nrf52840/nrf52832.ini

@@ -1,7 +1,9 @@
 [nrf52832_base]
 extends = nrf52_base
 
-build_flags = ${nrf52_base.build_flags} 
+build_flags =
+  ${nrf52_base.build_flags}
+  -DSERIAL_BUFFER_SIZE=1024
 
 lib_deps =
   ${nrf52_base.lib_deps}

variants/nrf52840/nrf52840.ini

@@ -1,7 +1,9 @@
 [nrf52840_base]
 extends = nrf52_base
 
-build_flags = ${nrf52_base.build_flags} 
+build_flags =
+   ${nrf52_base.build_flags}
+  -DSERIAL_BUFFER_SIZE=4096
 
 lib_deps =
   ${nrf52_base.lib_deps}