examples/proc_test: increase buffer size
examples/proc_test: increase buffer size

Depending on the way of how it is implemented, the output from a /proc
entry is truncated if too small buffer were passed from user. To avoid
this, we need to allocate output buffer long enough to hold the output.

Change-Id: Idb2949fa20abc25c7601c95fc32708a2b76e8c92
Signed-off-by: Junhwan Park <7fee488b6f78fc50b291ffc7d10428788977e877@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT